Hypothermia is reduced body temperature that happens when a body dissipates more heat than it absorbs. In humans, it is defined as a body core temperature below 35.0 °C (95.0 °F). Symptoms depend on the temperature; in mild hypothermia there is shivering and mental confusion. In moderate hypothermia shivering stops and confusion increases; in severe hypothermia, there may be paradoxical undressing, in which a person removes his or her clothing, as well as an increased risk of the heart stopping.[2]

Hypothermia has two main types of causes, it classically occurs from exposure to extreme cold.[1] It may also occur from any condition that decreases heat production or increases heat loss.[1] Commonly this includes alcohol intoxication but may also include low blood sugar, anorexia, and advanced age.[1][2]Body temperature is usually maintained near a constant level of 36.5–37.5 °C (97.7–99.5 °F) through thermoregulation.[2] Efforts to increase body temperature involve shivering, increased voluntary activity, and putting on warmer clothing.[2][3] Hypothermia may be diagnosed based on either a person's symptoms in the presence of risk factors or by measuring a person's core temperature.[2]

The treatment of mild hypothermia involves warm drinks, warm clothing, and physical activity; in those with moderate hypothermia, heating blankets and warmed intravenous fluids are recommended. People with moderate or severe hypothermia should be moved gently; in severe hypothermia, extracorporeal membrane oxygenation (ECMO) or cardiopulmonary bypass may be useful. In those without a pulse, cardiopulmonary resuscitation (CPR) is indicated along with the above measures. Rewarming is typically continued until a person's temperature is greater than 32 °C (90 °F). If there is no improvement at this point or the blood potassium level is greater than 12 mmol/liter at any time, resuscitation may be discontinued.[2]

Hypothermia is the cause of at least 1,500 deaths a year in the United States,[2] it is more common in older people and males.[4] One of the lowest documented body temperatures from which someone with accidental hypothermia has survived is 13.0 °C (55.4 °F) in a near-drowning of a 7-year-old girl in Sweden.[5] Survival after more than six hours of CPR has been described,[2] for those for whom ECMO or bypass is used, survival is around 50%.[2] Deaths due to hypothermia have played an important role in many wars,[1] the term is from Greek ὑπο, ypo, meaning "under", and θερμία, thermía, meaning "heat". The opposite of hypothermia is hyperthermia, an increased body temperature due to failed thermoregulation.[6][7]

Signs and symptoms

Signs and symptoms vary depending on the degree of hypothermia, and may be divided by the three stages of severity. Infants with hypothermia may feel cold when touched, with bright red skin and an unusual lack of energy.[12]

Moderate

Low body temperature results in shivering becoming more violent. Muscle mis-coordination becomes apparent.[18][19][20] Movements are slow and labored, accompanied by a stumbling pace and mild confusion, although the person may appear alert. Surface blood vessels contract further as the body focuses its remaining resources on keeping the vital organs warm, the subject becomes pale. Lips, ears, fingers, and toes may become blue.

Severe

As the temperature decreases, further physiological systems falter and heart rate, respiratory rate, and blood pressure all decrease. This results in an expected heart rate in the 30s at a temperature of 28 °C (82 °F).[15]

Difficulty speaking, sluggish thinking, and amnesia start to appear; inability to use hands and stumbling are also usually present. Cellular metabolic processes shut down. Below 30 °C (86 °F), the exposed skin becomes blue and puffy, muscle coordination very poor, and walking almost impossible, and the person exhibits incoherent or irrational behavior, including terminal burrowing (see below) or even stupor. Pulse and respiration rates decrease significantly, but fast heart rates (ventricular tachycardia, atrial fibrillation) can also occur. Atrial fibrillation is not typically a concern in and of itself.[2] Major organs fail and clinical death occurs.

Paradoxical undressing

Twenty to fifty percent of hypothermia deaths are associated with paradoxical undressing, this typically occurs during moderate and severe hypothermia, as the person becomes disoriented, confused, and combative. They may begin discarding their clothing, which, in turn, increases the rate of heat loss.[21][22]

Rescuers who are trained in mountain survival techniques are taught to expect this; however, people who die from hypothermia in urban environments are sometimes incorrectly assumed to have been subjected to sexual assault.[23]

One explanation for the effect is a cold-induced malfunction of the hypothalamus, the part of the brain that regulates body temperature. Another explanation is that the muscles contracting peripheral blood vessels become exhausted (known as a loss of vasomotor tone) and relax, leading to a sudden surge of blood (and heat) to the extremities, causing the person to feel overheated.[23][24]

Terminal burrowing

An apparent self-protective behaviour, known as "terminal burrowing&, or "hide-and-die syndrome",[25] occurs in the final stages of hypothermia. The afflicted will enter small, enclosed spaces, such as underneath beds or behind wardrobes, it is often associated with paradoxical undressing.[26] Researchers in Germany claim this is "obviously an autonomous process of the brain stem, which is triggered in the final state of hypothermia and produces a primitive and burrowing-like behavior of protection, as seen in hibernating animals."[27] This happens mostly in cases where temperature drops slowly.[24]

Causes

The rate of hypothermia is strongly related to age in the United States

Hypothermia usually occurs from exposure to low temperatures, and is frequently complicated by alcohol consumption.[1] Any condition that decreases heat production, increases heat loss, or impairs thermoregulation, however, may contribute.[1] Thus, hypothermia risk factors include: substance abuse (including alcohol abuse), homelessness, any condition that affects judgment (such as hypoglycemia), the extremes of age, poor clothing, chronic medical conditions (such as hypothyroidism and sepsis), and living in a cold environment.[28][29] Hypothermia occurs frequently in major trauma, and is also observed in severe cases of anorexia nervosa.

Alcohol

Alcohol consumption increases the risk of hypothermia by its action as a vasodilator, it increases blood flow to the skin and extremities, making a person feel warm, while increasing heat loss.[30] Between 33% and 73% of hypothermia cases are complicated by alcohol.[1]

Poverty

In the UK, 28,354 cases of hypothermia were treated in 2012-13 – an increase of 25% from the previous year,[31] some cases of hypothermia death, as well as other preventable deaths, happen because poor people cannot easily afford to keep warm. Rising fuel bills have increased the numbers who have difficulty paying for adequate heating in the UK, some pensioners and disabled people are at risk because they do not work and cannot easily get out of their homes. Better heat insulation can help.[32][33][34]

Water immersion

Two American marines participating in an immersion hypothermia exercise

Hypothermia continues to be a major limitation to swimming or diving in cold water,[18] the reduction in finger dexterity due to pain or numbness decreases general safety and work capacity, which consequently increases the risk of other injuries.[18][20]

Heat is lost much more quickly in water[18] than in air. Thus, water temperatures that would be quite reasonable as outdoor air temperatures can lead to hypothermia in survivors, although this is not usually the direct clinical cause of death for those who are not rescued. A water temperature of 10 °C (50 °F) can lead to death in as little as one hour, and water temperatures near freezing can cause death in as little as 15 minutes.[35] A notable example of this occurred during the sinking of the Titanic, when most people who entered the −2 °C (28 °F) water died in 15–30 minutes.[36]

The actual cause of death in cold water is usually the bodily reactions to heat loss and to freezing water, rather than hypothermia (loss of core temperature) itself, for example, plunged into freezing seas, around 20% of victims die within two minutes from cold shock (uncontrolled rapid breathing, and gasping, causing water inhalation, massive increase in blood pressure and cardiac strain leading to cardiac arrest, and panic); another 50% die within 15–30 minutes from cold incapacitation (inability to use or control limbs and hands for swimming or gripping, as the body "protectively" shuts down the peripheral muscles of the limbs to protect its core).[37] Exhaustion and unconsciousness cause drowning, claiming the rest within a similar time.[35]

Heat is primarily generated in muscle tissue, including the heart, and in the liver, while it is lost through the skin (90%) and lungs (10%).[13] Heat production may be increased two- to four-fold through muscle contractions (i.e. exercise and shivering).[13] The rate of heat loss is determined, as with any object, by convection, conduction, and radiation,[13] the rates of these can be affected by body mass index, body surface area to volume ratios, clothing and other environmental conditions.[42]

Research has shown that glomerular filtration rates (GFR) decrease as a result of hypothermia;[44] in essence, hypothermia increases preglomerular vasoconstriction, thus decreasing both renal blood flow (RBF) and GFR.[45]

Diagnosis

Accurate determination of core temperature often requires a special low temperature thermometer, as most clinical thermometers do not measure accurately below 34.4 °C (93.9 °F).[14] A low temperature thermometer can be placed in the rectum, esophagus or bladder. Esophageal measurements are the most accurate and are recommended once a person is intubated.[2] Other methods of measurement such as in the mouth, under the arm, or using an infrared ear thermometer are often not accurate.[2]

As a hypothermic person's heart rate may be very slow, prolonged feeling for a pulse could be required before detecting; in 2005, the American Heart Association recommended at least 30–45 seconds to verify the absence of a pulse before initiating CPR.[46] Others recommend a 60-second check.[2]

The classical ECG finding of hypothermia is the Osborn J wave. Also, ventricular fibrillation frequently occurs below 28 °C (82 °F) and asystole below 20 °C (68 °F).[13] The Osborn J may look very similar to those of an acute ST elevation myocardial infarction.[15] Thrombolysis as a reaction to the presence of Osborn J waves is not indicated, as it would only worsen the underlying coagulopathy caused by hypothermia.

Prevention

Appropriate clothing helps to prevent hypothermia. Synthetic and wool fabrics are superior to cotton as they provide better insulation when wet and dry. Some synthetic fabrics, such as polypropylene and polyester, are used in clothing designed to wick perspiration away from the body, such as liner socks and moisture-wicking undergarments. Clothing should be loose fitting, as tight clothing reduces the circulation of warm blood;[47] in planning outdoor activity, prepare appropriately for possible cold weather. Those who drink alcohol before or during outdoor activity should ensure at least one sober person is present responsible for safety.

Covering the head is effective, but no more effective than covering any other part of the body. While common folklore says that people lose most of their heat through their heads, heat loss from the head is no more significant than that from other uncovered parts of the body.[48][49] However, heat loss from the head is significant in infants, whose head is larger relative to the rest of the body than in adults. Several studies have shown that for uncovered infants, lined hats significantly reduce heat loss and thermal stress.[50][51][52] Children have a larger surface area per unit mass, and other things being equal should have one more layer of clothing than adults in similar conditions, and the time they spend in cold environments should be limited, however children are often more active than adults, and may generate more heat. In both adults and children, overexertion causes sweating and thus increases heat loss.[53]

Building a shelter can aid survival where there is danger of death from exposure. Shelters can be of many different types, metal can conduct heat away from the occupants and is sometimes best avoided, the shelter should not be too big so body warmth stays near the occupants. Good ventilation is essential especially if a fire will be lit in the shelter. Fires should be put out before the occupants sleep to prevent carbon monoxide poisoning. People caught in very cold, snowy conditions can build an igloo or snow cave to shelter.[54][55]

Management

Aggressiveness of treatment is matched to the degree of hypothermia.[2] Treatment ranges from noninvasive, passive external warming to active external rewarming, to active core rewarming;[14] in severe cases resuscitation begins with simultaneous removal from the cold environment and management of the airway, breathing, and circulation. Rapid rewarming is then commenced. Moving the person as little and as gently as possible is recommended as aggressive handling may increase risks of a dysrhythmia.[46]

The UK National Health Service advises the lay public against putting a person in a hot bath, massaging their arms and legs, using a heating pad, or giving them alcohol, these measures can cause blood to be directed to the skin, causing a fall in blood pressure to vital organs, potentially resulting in death.[60]

Rewarming

Rewarming can be done with a number of methods including passive external rewarming, active external rewarming, and active internal rewarming.[61] Passive external rewarming involves the use of a person's own ability to generate heat by providing properly insulated dry clothing and moving to a warm environment,[62] it is recommended for those with mild hypothermia.[62]

Active external rewarming involves applying warming devices externally, such as a heating blanket,[2] these may function by warmed forced air (Bair Hugger is a commonly used device), chemical reactions, or electricity.[2][62] In wilderness environments, hypothermia may be helped by placing hot water bottles in both armpits and in the groin,[63] these methods are recommended for moderate hypothermia.[62] Active core rewarming involves the use of intravenous warmed fluids, irrigation of body cavities with warmed fluids (the chest or abdomen), use of warm humidified inhaled air, or use of extracorporeal rewarming such as via a heart lung machine or extracorporeal membrane oxygenation (ECMO).[61] Extracorporeal rewarming is the fastest method for those with severe hypothermia.[62] Survival rates with normal mental functioning have been reported at around 50%.[2] Chest irrigation is recommended if bypass or ECMO is not possible.[2]

Rewarming shock (or rewarming collapse) is a sudden drop in blood pressure in combination with a low cardiac output which may occur during active treatment of a severely hypothermic person.[64][65] There was a theoretical concern that external rewarming rather than internal rewarming may increase the risk,[2] these concerns were partly believed to be due to afterdrop, a situation detected during laboratory experiments where there is a continued decrease in core temperature after rewarming has been started.[2] Recent studies have not supported these concerns, and problems are not found with active external rewarming.[2][46]

Fluids

Warm sweetened liquids can be given provided the person is alert and can swallow. Many recommend that alcohol[27][57] and drinks with lots of caffeine be avoided,[66] as most people are moderately dehydrated due to cold-induced diuresis, warmed intravenous fluids to a temperature of 38–45 °C (100–113 °F) are often recommended.[2][14]

Prognosis

It is usually recommended not to declare a person dead until their body is warmed to a near normal body temperature of greater than 32 °C (90 °F),[2] since extreme hypothermia can suppress heart and brain function.[68] Exceptions include if there is an obvious fatal injuries or the chest is frozen so that it cannot be compressed.[46] If a person was buried in an avalanche for more than 35 minutes and is found with a mouth packed full of snow without a pulse, stopping early may also be reasonable,[2] this is also the case if a person's blood potassium is greater than 12 mmol/l.[2]

Those who are stiff with pupils that do not move may survive if treated aggressively.[2] Survival with good function also occasionally occurs even after the need for hours of CPR.[2] Children who have near-drowning accidents in water near 0 °C (32 °F) can occasionally be revived, even over an hour after losing consciousness.[69] The cold water lowers the metabolism, allowing the brain to withstand a much longer period of hypoxia. While survival is possible, mortality from severe or profound hypothermia remains high despite optimal treatment. Studies estimate mortality at between 38%[70][71] and 75%.[13]

In those who have hypothermia due to another underlying health problem, when death occurs it is frequently from that underlying health problem.[2]

Epidemiology

In the past, hypothermia occurred most frequently in homeless people, but recreational exposure to cold environments is now the main cause of hypothermia. Between 1995 and 2004 in the United States, an average of 1560 cold-related emergency department visits occurred per year and in the years 1999 to 2004, an average of 647 people died per year due to hypothermia.[28][72]

History

Hypothermia has played a major role in the success or failure of many military campaigns, from Hannibal's loss of nearly half his men in the Second Punic War (218 B.C.) to the near destruction of Napoleon's armies in Russia in 1812. Men wandered around confused by hypothermia, some lost consciousness and died, others shivered, later developed torpor, and tended to sleep. Others too weak to walk fell on their knees; some stayed that way some time resisting death. The pulse of some was weak and hard to detect; others groaned; yet others had eyes open and wild with quiet delirium.[73] Loss of life to hypothermia in Russian regions continued through the first and second world wars, especially in the Battle of Stalingrad.[74]

Antarctic explorers developed hypothermia; Ernest Shackleton and his team measured body temperatures "below 94.2°, which spells death at home", though this probably referred to oral temperatures rather than core temperature and corresponded to mild hypothermia. One of Scott's team, Atkinson, became confused through hypothermia.[73]

Nazi human experimentation during World War II amounting to medical torture included hypothermia experiments, which killed many victims. There were 360 to 400 experiments and 280 to 300 subjects, indicating some had more than one experiment performed on them. Various methods of rewarming were attempted, "One assistant later testified that some victims were thrown into boiling water for rewarming".[78]

Other animals

Many animals other than humans often induce hypothermia during hibernation or torpor.

Water bears (Tardigrade), microscopic multicellular organisms, can survive freezing at low temperatures by replacing most of their internal water with the sugartrehalose, preventing the crystallization that otherwise damages cell membranes.

1.
Critical care medicine
–
They may also be admitted for intensive/invasive monitoring, such as the crucial hours after major surgery when deemed too unstable to transfer to a less intensively monitored unit. Intensive care is only offered to those whose condition is potentially reversible. A prime requisite for admission to an intensive care unit is that the condition can be overcome. Medical studies suggest a relation between ICU volume and quality of care for mechanically ventilated patients, after adjustment for severity of illness, demographic variables, and characteristics of the ICUs, higher ICU volume was significantly associated with lower ICU and hospital mortality rates. For example, adjusted ICU mortality was 21. 2% in hospitals with 87 to 150 mechanically ventilated patients annually, hospitals with intermediate numbers of patients had outcomes between these extremes. This may include interpreting machine noises as human voices, seeing walls quiver, in general, it is the most expensive, technologically advanced and resource-intensive area of medical care. In the United States, estimates of the 2000 expenditure for critical care medicine ranged from US$15–55 billion, during that year, critical care medicine accounted for 0. 56% of GDP,4. 2% of national health expenditure and about 13% of hospital costs. In 2011 hospital stays with ICU services accounted for just over one-quarter of all discharges, the mean hospital charge was 2.5 times higher for discharges with ICU services than for those without. Intensive care usually takes a system by system approach to treatment, the nine key systems are each considered on an observation-intervention-impression basis to produce a daily plan. As well as the key systems, intensive care treatment raises other issues including health, pressure points, mobilisation and physiotherapy. The nine key IC systems are, cardiovascular system, central nervous system, endocrine system, gastro-intestinal tract, hematology, microbiology, peripheries, renal, and respiratory system. The provision of care is, in general, administered in a specialized unit of a hospital called the intensive care unit or critical care unit. The naming is not rigidly standardized, Critical care medicine is a relatively new but increasingly important medical specialty. Physicians with training in critical care medicine are referred to as intensivists, US board certification in critical care medicine is available through all five specialty boards. The American Society of Critical Care Medicine is a well-established multiprofessional society for working in the ICU including nurses, respriatory therapists. Most medical research has demonstrated that ICU care provided by intensivists produces better outcomes and this has led the Leapfrog Group to make a primary recommendation that all ICU patients be managed or co-managed by a dedicated intensivist who is exclusively responsible for patients in one ICU. However, in the US, there is a shortage of intensivists. Other members of the care team may also pursue additional training in critical care medicine as intensivists

2.
Diagnostic method
–
Medical diagnosis is the process of determining which disease or condition explains a persons symptoms and signs. It is most often referred to as diagnosis with the context being implicit. The information required for diagnosis is typically collected from a history, often, one or more diagnostic procedures, such as diagnostic tests, are also done during the process. Sometimes Posthumous diagnosis is considered a kind of medical diagnosis, Diagnosis is often challenging, because many signs and symptoms are nonspecific. For example, redness of the skin, by itself, is a sign of many disorders, thus differential diagnosis, in which several possible explanations are compared and contrasted, must be performed. This involves the correlation of various pieces of information followed by the recognition and differentiation of patterns, occasionally the process is made easy by a sign or symptom that is pathognomonic. Diagnosis is a component of the procedure of a doctors visit. From the point of view of statistics, the procedure involves classification tests. The first recorded examples of medical diagnosis are found in the writings of Imhotep in ancient Egypt, a Babylonian medical textbook, the Diagnostic Handbook written by Esagil-kin-apli, introduced the use of empiricism, logic and rationality in the diagnosis of an illness or disease. Traditional Chinese Medicine, as described in the Yellow Emperors Inner Canon or Huangdi Neijing, specified four diagnostic methods, inspection, auscultation-olfaction, interrogation, hippocrates was known to make diagnoses by tasting his patients urine and smelling their sweat. This article uses diagnostician as any of these person categories, a diagnostic procedure does not necessarily involve elucidation of the etiology of the diseases or conditions of interest, that is, what caused the disease or condition. Such elucidation can be useful to optimize treatment, further specify the prognosis or prevent recurrence of the disease or condition in the future, the initial task is to detect a medical indication to perform a diagnostic procedure. Indications include, Detection of any deviation from what is known to be normal, such as can be described in terms of, for example, anatomy, physiology, pathology, psychology, a complaint expressed by a patient. The fact that a patient has sought a diagnostician can itself be an indication to perform a diagnostic procedure, even during an already ongoing diagnostic procedure, there can be an indication to perform another, separate, diagnostic procedure for another, potentially concomitant, disease or condition. A diagnostic test is any kind of medical test performed to aid in the diagnosis or detection of disease, Diagnostic tests can also be used to provide prognostic information on people with established disease. Processing of the answers, findings or other results, consultations with other providers and specialists in the field may be sought. There are a number of methods or techniques that can be used in a diagnostic procedure, in reality, a diagnostic procedure may involve components of multiple methods. The final result may also remain a list of possible conditions, the resultant diagnostic opinion by this method can be regarded more or less as a diagnosis of exclusion

Diagnostic method
–
Radiography is an important tool in diagnosis of certain disorders.

3.
Body temperature
–
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature as its own body temperature, the internal thermoregulation process is one aspect of homeostasis, a state of dynamic stability in an organisms internal conditions, maintained far from thermal equilibrium with its environment. If the body is unable to maintain a temperature and it increases significantly above normal. For humans, this occurs when the body is exposed to constant temperatures of approximately 55 °C, humans may also experience lethal hyperthermia when the wet bulb temperature is sustained above 35 °C for six hours. The opposite condition, when temperature decreases below normal levels, is known as hypothermia. It was not until the introduction of thermometers that any data on the temperature of animals could be obtained. Hence it is important to identify the parts of the body that most closely reflect the temperature of the internal organs, also, for such results to be comparable, the measurements must be conducted under comparable conditions. The rectum has traditionally been considered to reflect most accurately the temperature of internal parts, or in cases of sex or species. Occasionally the temperature of the urine as it leaves the urethra may be of use in measuring body temperature, more often the temperature is taken in the mouth, axilla, ear or groin. Some animals undergo one of forms of dormancy where the thermoregulation process temporarily allows the body temperature to drop. Examples include hibernating bears and torpor in bats, thermoregulation in organisms runs along a spectrum from endothermy to ectothermy. Endotherms create most of their heat via metabolic processes, and are referred to as warm-blooded. Ectotherms use external sources of temperature to regulate their body temperatures and they are colloquially referred to as cold-blooded despite the fact that body temperatures often stay within the same temperature ranges as warm-blooded animals. Ectotherms are the opposite of endotherms when it comes to regulating internal temperatures, in ectotherms, the internal physiological sources of heat are of negligible importance, the biggest factor that enables them to maintain adequate body temperatures is due to environmental influences. Vaporization, Evaporation of sweat and other bodily fluids, convection, Increasing blood flow to body surfaces to maximize heat loss. Conduction, Losing heat by being in contact with a colder surface, for instance, Lying on cool ground. Staying wet in a river, lake or sea, radiation, releasing heat by radiating it away from the body. Convection, Climbing to higher ground up trees, ridges, rocks, entering a warm water or air current

Body temperature
–
Thermoregulation in animals
Body temperature
–
Seeking shade is one method of cooling. Here sooty tern chicks are using a black-footed albatross chick for shade.
Body temperature
–
Thermographic image of a snake around an arm
Body temperature
–
Kangaroo licking its arms to cool down on a very hot day

4.
Core temperature
–
Normal human body temperature, also known as normothermia or euthermia, is the typically temperature range found in humans. The normal human body temperature range is stated as 36. 5–37.5 °C. It is typically maintained within this range by thermoregulation, human body temperature is of interest in medical practice, human reproduction, and athletics. Taking a persons temperature is an part of a full clinical examination. In humans, the internal temperature is 37.0 °C. However, no person always has exactly the same temperature at every moment of the day, temperatures cycle regularly up and down through the day, as controlled by the persons circadian rhythm. The lowest temperature occurs about two hours before the person wakes up. Additionally, temperatures change according to activities and external factors, normal human body temperature varies slightly from person to person and by the time of day. Consequently, each type of measurement has a range of normal temperatures, the range for normal human body temperatures, taken orally, is 36. 8±0.5 °C. This means that any oral temperature between 36.3 and 37.3 °C is likely to be normal, the normal human body temperature is often stated as 36. 5–37.5 °C. In adults a review of the literature has found a range of 33. 2–38.2 °C for normal temperatures, depending on the gender. Reported values vary depending on how it is measured, oral,36. 8±0.4 °C, a rectal or vaginal measurement taken directly inside the body cavity is typically slightly higher than oral measurement, and oral measurement is somewhat higher than skin measurement. Other places, such as under the arm or in the ear, while some people think of these averages as representing normal or ideal measurements, a wide range of temperatures has been found in healthy people. Other circumstances also affect the bodys temperature, the body temperature also changes when a person is hungry, sleepy, sick, or cold. An individuals body temperature changes by about 0.5 °C between its highest and lowest points each day. Body temperature is sensitive to hormones, so women have a temperature rhythm that varies with the menstrual cycle. A womans basal body temperature rises sharply after ovulation, as estrogen production decreases, fertility awareness programs use this change to identify when a woman has ovulated in order to achieve or avoid pregnancy. During the luteal phase of the cycle, both the lowest and the average temperatures are slightly higher than during other parts of the cycle

5.
Thermoregulation
–
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature as its own body temperature, the internal thermoregulation process is one aspect of homeostasis, a state of dynamic stability in an organisms internal conditions, maintained far from thermal equilibrium with its environment. If the body is unable to maintain a temperature and it increases significantly above normal. For humans, this occurs when the body is exposed to constant temperatures of approximately 55 °C, humans may also experience lethal hyperthermia when the wet bulb temperature is sustained above 35 °C for six hours. The opposite condition, when temperature decreases below normal levels, is known as hypothermia. It was not until the introduction of thermometers that any data on the temperature of animals could be obtained. Hence it is important to identify the parts of the body that most closely reflect the temperature of the internal organs, also, for such results to be comparable, the measurements must be conducted under comparable conditions. The rectum has traditionally been considered to reflect most accurately the temperature of internal parts, or in cases of sex or species. Occasionally the temperature of the urine as it leaves the urethra may be of use in measuring body temperature, more often the temperature is taken in the mouth, axilla, ear or groin. Some animals undergo one of forms of dormancy where the thermoregulation process temporarily allows the body temperature to drop. Examples include hibernating bears and torpor in bats, thermoregulation in organisms runs along a spectrum from endothermy to ectothermy. Endotherms create most of their heat via metabolic processes, and are referred to as warm-blooded. Ectotherms use external sources of temperature to regulate their body temperatures and they are colloquially referred to as cold-blooded despite the fact that body temperatures often stay within the same temperature ranges as warm-blooded animals. Ectotherms are the opposite of endotherms when it comes to regulating internal temperatures, in ectotherms, the internal physiological sources of heat are of negligible importance, the biggest factor that enables them to maintain adequate body temperatures is due to environmental influences. Vaporization, Evaporation of sweat and other bodily fluids, convection, Increasing blood flow to body surfaces to maximize heat loss. Conduction, Losing heat by being in contact with a colder surface, for instance, Lying on cool ground. Staying wet in a river, lake or sea, radiation, releasing heat by radiating it away from the body. Convection, Climbing to higher ground up trees, ridges, rocks, entering a warm water or air current

Thermoregulation
–
Thermoregulation in animals
Thermoregulation
–
Seeking shade is one method of cooling. Here sooty tern chicks are using a black-footed albatross chick for shade.
Thermoregulation
–
Thermographic image of a snake around an arm
Thermoregulation
–
Kangaroo licking its arms to cool down on a very hot day

6.
Pulse
–
In medicine, a pulse represents the tactile arterial palpation of the heartbeat by trained fingertips. Pulse is equivalent to measuring the heart rate, the heart rate can also be measured by listening to the heart beat directly, traditionally using a stethoscope and counting it for a minute. The radial pulse is measured using three fingers. The study of the pulse is known as sphygmology, the pulse is a decidedly low tech and high yield and antiquated term still useful at the bedside in an age of computational analysis of cardiac performance. Claudius Galen was perhaps the first physiologist to describe the pulse, the pulse is an expedient tactile method of determination of systolic blood pressure to a trained observer. Diastolic blood pressure is non-palpable and unobservable by tactile methods, occurring between heartbeats, pressure waves generated by the heart in systole move the arterial walls. Forward movement of blood occurs when the boundaries are pliable and compliant and these properties form enough to create a palpable pressure wave. The heart rate may be greater or lesser than the pulse rate depending upon physiologic demand, in this case, the heart rate is determined by auscultation or audible sounds at the heart apex, in which case it is not the pulse. The pulse deficit is determined by simultaneous palpation at the artery and auscultation at the PMI. It may be present in case of premature beats or atrial fibrillation, pulse velocity, pulse deficits and much more physiologic data are readily and simplistically visualized by the use of one or more arterial catheters connected to a transducer and oscilloscope. This invasive technique has been used in intensive care since the 1970s. The rate of the pulse is observed and measured by tactile or visual means on the outside of an artery and is recorded as beats per minute or BPM, the pulse may be further indirectly observed under light absorbances of varying wavelengths with assigned and inexpensively reproduced mathematical ratios. Applied capture of variances of light signal from the blood component hemoglobin under oxygenated vs. deoxygenated conditions allows the technology of pulse oximetry, normal pulse rates at rest, in beats per minute, The pulse rate can be used to check overall heart health and fitness level. Generally lower is better, but bradycardias can be dangerous, symptoms of a dangerously slow heartbeat include weakness, loss of energy and fainting. A normal pulse is regular in rhythm and force, an irregular pulse may be due to sinus arrhythmia, ectopic beats, atrial fibrillation, paroxysmal atrial tachycardia, atrial flutter, partial heart block etc. Intermittent dropping out of beats at pulse is called intermittent pulse, examples of regular intermittent pulse include pulsus bigeminus, second-degree atrioventricular block. An example of irregular intermittent pulse is atrial fibrillation, the degree of expansion displayed by artery during diastolic and systolic state is called volume. It is also known as amplitude, expansion or size of pulse, a weak pulse signifies narrow pulse pressure

Pulse
–
Pulse evaluation at the radial artery.

7.
Normal human body temperature
–
Normal human body temperature, also known as normothermia or euthermia, is the typically temperature range found in humans. The normal human body temperature range is stated as 36. 5–37.5 °C. It is typically maintained within this range by thermoregulation, human body temperature is of interest in medical practice, human reproduction, and athletics. Taking a persons temperature is an part of a full clinical examination. In humans, the internal temperature is 37.0 °C. However, no person always has exactly the same temperature at every moment of the day, temperatures cycle regularly up and down through the day, as controlled by the persons circadian rhythm. The lowest temperature occurs about two hours before the person wakes up. Additionally, temperatures change according to activities and external factors, normal human body temperature varies slightly from person to person and by the time of day. Consequently, each type of measurement has a range of normal temperatures, the range for normal human body temperatures, taken orally, is 36. 8±0.5 °C. This means that any oral temperature between 36.3 and 37.3 °C is likely to be normal, the normal human body temperature is often stated as 36. 5–37.5 °C. In adults a review of the literature has found a range of 33. 2–38.2 °C for normal temperatures, depending on the gender. Reported values vary depending on how it is measured, oral,36. 8±0.4 °C, a rectal or vaginal measurement taken directly inside the body cavity is typically slightly higher than oral measurement, and oral measurement is somewhat higher than skin measurement. Other places, such as under the arm or in the ear, while some people think of these averages as representing normal or ideal measurements, a wide range of temperatures has been found in healthy people. Other circumstances also affect the bodys temperature, the body temperature also changes when a person is hungry, sleepy, sick, or cold. An individuals body temperature changes by about 0.5 °C between its highest and lowest points each day. Body temperature is sensitive to hormones, so women have a temperature rhythm that varies with the menstrual cycle. A womans basal body temperature rises sharply after ovulation, as estrogen production decreases, fertility awareness programs use this change to identify when a woman has ovulated in order to achieve or avoid pregnancy. During the luteal phase of the cycle, both the lowest and the average temperatures are slightly higher than during other parts of the cycle

8.
Vasoconstriction
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Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vessels, the process is particularly important in staunching hemorrhage and acute blood loss. When blood vessels constrict, the flow of blood is restricted or decreased and this makes the skin turn paler because less blood reaches the surface, reducing the radiation of heat. On a larger level, vasoconstriction is one mechanism by which the body regulates, medications causing vasoconstriction, also known as vasoconstrictors, are one type of medicine used to raise blood pressure. Generalized vasoconstriction usually results in an increase in blood pressure. The extent of vasoconstriction may be slight or severe depending on the substance or circumstance, many vasoconstrictors also cause pupil dilation. Medications that cause vasoconstriction include, antihistamines, decongestants, and stimulants, severe vasoconstriction may result in symptoms of intermittent claudication. The mechanism that leads to results from the increased concentration of calcium within vascular smooth muscle cells. However, the mechanisms for generating an increased intracellular concentration of calcium depends on the vasoconstrictor. Smooth muscle cells are capable of generating action potentials, but this mechanism is utilized for contraction in the vasculature. Hormonal or pharmokinetic components are more physiologically relevant, two common stimuli for eliciting smooth muscle contraction are circulating epinephrine and activation of the sympathetic nervous system that directly innervates the muscle. These compounds interact with cell surface adrenergic receptors, the rise in intracellular calcium complexes with calmodulin, which in turn activates myosin light-chain kinase. This enzyme is responsible for phosphorylating the light chain of myosin to stimulate cross-bridge cycling and this reduction in calcium removes the stimulus necessary for contraction, allowing for a return to baseline. Factors that trigger vasoconstriction can be of exogenous or endogenous origin, ambient temperature is an example of the former. Cutaneous vasoconstriction will occur because of the exposure to the severe cold. Examples of endogenous factors include the nervous system, circulating hormones. Examples include amphetamines, antihistamines and cocaine, many are used in medicine to treat hypotension and as topical decongestants. Vasoconstrictors are also used clinically to increase blood pressure or to reduce blood flow

9.
Diuresis
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Diuresis is increased urination and the physiologic process that produces such an increase. It involves extra urine production in the kidneys as part of the bodys maintenance of fluid balance. In healthy people, the drinking of water produces mild diuresis to maintain the body water balance. Many people with problems such as heart failure and kidney failure need diuretic medications to help their kidneys deal with the fluid overload of edema. These drugs help the body rid itself of water via the extra urine. Sometimes a connotative difference is felt between diuresis in the sense of appropriate increase and polyuria in the sense of inappropriate increase, however, sometimes the words are simply synonymous. Osmotic diuresis is the increase of urination caused by the presence of certain substances in the small tubes of the kidneys. The excretion occurs when substances such as enter the kidney tubules. The substances cause an increase in the pressure within the tubule, causing retention of water within the lumen. The same effect can be seen in such as mannitol. Substances in the circulation can also increase the amount of circulating fluid by increasing the osmolarity of the blood and this has the effect of pulling water from the interstitial space, making more water available in the blood and causing the kidney to compensate by removing it as urine. As blood pressure increases, the kidney removes the excess fluid as urine, sodium, chloride, potassium are excreted in Osmotic diuresis, originating from Diabetes Mellitus. Osmotic diuresis results in dehydration from polyuria and the classic polydipsia associated with DM, forced diuresis may enhance the excretion of certain drugs in urine and is used to treat drug overdose or poisoning of these drugs and hemorrhagic cystitis. Most of the drugs are weak acids or weak bases. When urine is made alkaline, elimination of drugs in the urine is increased. The converse applies for alkaline drugs, for acidic drugs, urine pH should be above the pK value of that drug, and converse for the basic drugs. It is because the ionization of acidic drug is increased in alkaline urine and this method is ineffective for drugs which are strongly protein bound or which have a large apparent volume of distribution. For forced alkaline diuresis, sodium bicarbonate is added to the fluid to make blood and, in turn

10.
Insulin
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Insulin is a peptide hormone produced by beta cells of the pancreatic islets. It regulates the metabolism of carbohydrates, fats and protein by promoting the absorption of, especially, glucose from the blood into fat, liver and skeletal muscle cells. In these tissues the absorbed glucose is converted into either glycogen via glycogenesis or fats via lipogenesis, or, in the case of the liver, Glucose production by the liver is strongly inhibited by high concentrations of insulin in the blood. Circulating insulin also affects the synthesis of proteins in a variety of tissues. It is therefore an anabolic hormone, promoting the conversion of small molecules in the blood into large molecules inside the cells, low insulin levels in the blood have the opposite effect by promoting widespread catabolism. Pancreatic beta cells are known to be sensitive to concentrations in the blood. When glucose concentrations in the blood are high, the pancreatic β cells secrete insulin into the blood, glucagon, through stimulating the liver to release glucose by glycogenolysis and gluconeogenesis, has the opposite effect of insulin. If pancreatic beta cells are destroyed by an reaction, insulin can no longer be synthesized or be secreted into the blood. This results in type 1 diabetes mellitus, which is characterized by high blood glucose concentrations. In type 2 diabetes mellitus the destruction of cells is less pronounced than in type 1 diabetes. Instead there is an accumulation of amyloid in the pancreatic islets, Type 2 diabetes is characterized by high rates of glucagon secretion into the blood which are unaffected by, and unresponsive to the concentration of glucose in the blood glucose. Insulin is still secreted into the blood in response to the blood glucose, as a result, the insulin levels, even when the blood sugar level is normal, are much higher than they are in healthy persons. There are a variety of treatment regimens, none of which is entirely satisfactory, when the pancreas’s capacity to secrete insulin can no longer keep the blood sugar level within normal bounds, insulin injections are given. The human insulin protein is composed of 51 amino acids, and has a mass of 5808 Da. It is a dimer of an A-chain and a B-chain, which are linked together by disulfide bonds, insulins structure varies slightly between species of animals. Insulin from animal sources differs somewhat in effectiveness from human insulin because of these variations, porcine insulin is especially close to the human version, and was widely used to treat type 1 diabetics before human insulin could be produced in large quantities by recombinant DNA technologies. The crystal structure of insulin in the state was determined by Dorothy Hodgkin. It is on the WHO Model List of Essential Medicines, the most important medications needed in a health system

Insulin
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High-resolution model of six insulin molecules assembled in a hexamer, highlighting the threefold symmetry, the zinc ion holding it together (pink sphere), and the histidine residues (pink sticks) involved in zinc binding. Inactive insulin is stored in the body as a hexamer, while the active form is the monomer.
Insulin
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SS-linked insulin monomer
Insulin
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A vial of insulin. It has been given a trade name, Actrapid, by the manufacturer.
Insulin
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The structure of insulin. The left side is a space-filling model of the insulin monomer, believed to be biologically active. Carbon is green, hydrogen white, oxygen red, and nitrogen blue. On the right side is a ribbon diagram of the insulin hexamer, believed to be the stored form. A monomer unit is highlighted with the A chain in blue and the B chain in cyan. Yellow denotes disulfide bonds, and magenta spheres are zinc ions.

11.
Trauma triad of death
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The trauma triad of death is a medical term describing the combination of hypothermia, acidosis and coagulopathy. This combination is seen in patients who have sustained severe traumatic injuries. Commonly when someone presents with these signs damage control surgery is employed to reverse the effects, the three conditions share a complex relationship, each factor can compound the others, resulting in high mortality if this positive feedback loop continues uninterrupted. Severe haemorrhage in trauma diminishes oxygen delivery, and may lead to hypothermia and this in turn can halt the coagulation cascade, preventing blood from clotting. Such an increase in acidity damages the tissues and organs of the body and can reduce myocardial performance, mohr, Alicia M. Asensio, Juan A. García-Núñez, Luis M. Petrone, Patrizio, Sifri, Ziad C. Guidelines for the Institution of Damage Control in Trauma Patients, ITACCS,15, 185–188

Trauma triad of death
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Triad of death

12.
Underwater diving
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Underwater diving is the practice of descending below the waters surface to conduct underwater activities. The saturation diving technique reduces the risk of decompression sickness after long duration deep dives, Atmospheric diving suits may be used to isolate the diver from the effects of high ambient pressure. Although not usually considered to be diving, crewed submersibles can extend depth range, Diving is also restricted to conditions which are not excessively hazardous, though the level of risk acceptable to the diver can vary considerably. Occasionally diving may be done in other than water. Recreational diving, sometimes called sport diving or subaquatics, is a leisure activity. Technical diving is a form of diving that achieves greater depths or endurance in more challenging conditions. Professional diving takes a range of diving activities to the work site. Public safety diving is the work done by law enforcement, fire rescue, and search & rescue/recovery dive teams. Military diving includes combat diving, clearance diving and ships husbandry diving, underwater sports is a group of competitive sports using either free-diving, snorkeling or scuba technique, or a combination of these techniques. The term deep sea diving refers to underwater diving, usually with surface supplied equipment, hard hat diving is any form of diving with a helmet, including the standard copper helmet, and other forms of free-flow and lightweight demand helmets. There are several modes of diving based on the equipment used. The ability to dive and swim underwater while holding ones breath is considered a useful skill, an important part of water sport and Navy safety training. Underwater diving without breathing apparatus can be categorized as underwater swimming, snorkeling and freediving. Several competitive underwater sports are practiced without breathing apparatus, freediving precludes the use of external breathing devices, and relies on the ability of divers to hold their breath until resurfacing. The technique ranges from simple breath-hold diving to competitive apnea dives, fins and a diving mask are often used in free diving to improve vision and provide more efficient propulsion. A short breathing tube called a snorkel allows the diver to breathe at the surface while the face is immersed, snorkeling on the surface with no intention of diving is a popular water sport and recreational activity. Scuba diving is diving with an underwater breathing apparatus, which is completely independent of surface supply. Scuba provides the diver with the advantages of mobility and horizontal range far beyond the reach of a hose attached to surface-supplied diving equipment

Underwater diving
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A U.S. Navy diver enters the water during a training evaluation
Underwater diving
Underwater diving
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Museum of Diving in Warsaw
Underwater diving
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Natural sponges have been harvested by free divers near the Greek island of Kalymnos since at least the time of Plato.

13.
Dry suit
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A dry suit normally protects the whole body except the head, hands, and possibly the feet. In hazmat configurations, however, all of these are covered as well, the main difference between dry suits and wetsuits is that dry suits are designed to prevent water entering. This generally allows better insulation making them suitable for use in cold water. Dry suits can be hot in warm or hot air. Dry suits provide passive thermal protection, They insulate against heat transfer to the environment, an inflation valve with gas supply and dump valve are generally provided, but were not standard on early models. The main part of the dry suit is a shell made from a membrane type material. Membrane dry suits are made from materials which have little thermal insulation. They are commonly made of stockinette fabric coated with vulcanized rubber, laminated layers of nylon, to stay warm in a membrane suit, the wearer must wear an insulating undersuit, today typically made with polyester or other synthetic fiber batting. Polyester and other synthetics are preferred over natural materials, since synthetic materials have better insulating properties when damp or wet from sweat, seepage, or a leak. Reasonable care must be not to puncture or tear membrane dry suits, because buoyancy. The dry suit material offers essentially no buoyancy or insulation itself, so if the dry suit leaks or is torn, water can soak the undersuit, with a loss of buoyancy. Membrane dry suits may also be made of a waterproof but breathable material like Gore-Tex to enable comfortable wear without excessive humidity and this function does not work underwater. Sailors and boaters who intend to stay out of the water may prefer this type of suit, wetsuits are made from this material as it is a good insulator, waterproof, and is flexible enough for comfortable wear. The neoprene alone is very flexible, but not very resistant to tearing, so it is skinned with a layer of knit fabric bonded to each side for strength and abrasion resistance. Foamed neoprene may be used for the shell of a drysuit, providing some insulation due to the gas within the material, as with wet suits, their buoyancy and thermal protection decreases with depth as the air bubbles in the neoprene are compressed. Foam-neoprene tends to shrink over the years as it loses gas from the foam, an alternative is crushed or compressed foam neoprene, which is less susceptible to volume changes when under pressure. Some suits marketed as hybrid suits combine the features of types, with a membrane top attached to a neoprene bottom near the waist. The neoprene part is usually configured as a sleeveless farmer-john that covers the torso as well and this style is often used for surface water sports, especially in very cold water

Dry suit
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The neck seal, the zip, the inflator, a wrist seal, and the manual vent of a neoprene dry suit
Dry suit
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Low pressureair hose for the dry suit, CEJN type
Dry suit
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Membrane drysuit in icy water
Dry suit
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Dry suit diver just out of the water.

14.
Thermal insulation
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Thermal insulation is the reduction of heat transfer between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with specially engineered methods or processes, as well as with suitable object shapes, heat flow is an inevitable consequence of contact between objects of differing temperature. Thermal insulation provides a region of insulation in which thermal conduction is reduced or thermal radiation is reflected rather than absorbed by the lower-temperature body, the insulating capability of a material is measured with thermal conductivity. Low thermal conductivity is equivalent to high insulating capability, in thermal engineering, other important properties of insulating materials are product density and specific heat capacity. Solid materials chosen for insulation have a low thermal conductivity k, as the thickness of insulation is increased, the thermal resistance also increases. For insulated cylinders, a critical radius must be reached, before the critical radius is reached any added insulation increases heat transfer. If the outside radius of a cylinder is increased by applying insulation, however, at the same time, the convective resistance is reduced. This implies that adding insulation below a critical radius actually increases the heat transfer. If the radius of the cylinder is smaller than the critical radius for insulation. Gases possess poor thermal conduction properties compared to liquids and solids, in order to further augment the effectiveness of a gas it may be disrupted into small cells which cannot effectively transfer heat by natural convection. Convection involves a larger flow of gas driven by buoyancy and temperature differences. In order to accomplish gas cell formation in man-made thermal insulation, glass and this principle is used industrially in building and piping insulation such as, cellulose, rock wool, polystyrene foam, urethane foam, vermiculite, perlite, and cork. Trapping air is also the principle in all highly insulating clothing materials such as wool, down feathers, the air-trapping property is also the insulation principle employed by homeothermic animals to stay warm, for example down feathers, and insulating hair such as natural sheeps wool. In both cases the primary insulating material is air, and the used for trapping the air is natural keratin protein. Maintaining acceptable temperatures in buildings uses a proportion of global energy consumption. For a period of time, Asbestos was also used, however, when well insulated, a building, is energy-efficient, thus saving the owner money. Provides more uniform throughout the space. Unlike heating and cooling equipment, insulation is permanent and does not require maintenance, upkeep, lowers the carbon footprint of a building

15.
Cold shock response
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Cold shock response is the physiological response of organisms to sudden cold, especially cold water. In humans, cold shock response is perhaps the most common cause of death from immersion in cold water. The immediate shock of the cold causes involuntary inhalation, which if underwater can result in drowning, the cold water can also cause heart attack due to vasoconstriction, the heart has to work harder to pump the same volume of blood throughout the body. For people with disease, this additional workload can cause the heart to go into arrest. Inhalation of water may result from hyperventilation, some people are much better able to survive swimming in very cold water due to body or mental conditioning. Hypothermia from exposure to water is not as sudden as is often believed. A person who survives the initial minute of trauma, can survive for at least thirty minutes provided they dont drown, however, the ability to perform useful work declines substantially after ten minutes. It is possible to undergo physiological conditioning to reduce the shock response. In these ways, winter swimmers can survive both the initial shock and prolonged exposure, nevertheless, the human organism is not suited to freezing water, the struggle to maintain blood temperature produces great fatigue after thirty minutes or less. Bacteria express a set of proteins after a rapid decrease in temperature. Cold shock proteins may include helicases, nucleases, and ribosome-associated components that interact with DNA and RNA, processes such as cold signal perception, membrane adaptation, and the modification of the translation apparatus are involved. Hypothermia Diving reflex Introduction to Frozen Mythbusters and Myth #1

16.
Panic
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Panic may occur singularly in individuals or manifest suddenly in large groups as mass panic. The word derives from antiquity and is a tribute to the ancient god, one of the many gods in the mythology of ancient Greece, Pan was the god of shepherds and of woods and pastures. From this aspect of Pans nature Greek authors derived the word panikon, “sudden fear, ” the ultimate source of the English word, prehistoric humans used mass panic as a technique when hunting animals, especially ruminants. Herds reacting to unusually strong sounds or unfamiliar visual effects were directed towards cliffs, the most effective methods are often non-intuitive. An influential theoretical treatment of panic is found in Neil J. Smelsers Theory of Collective Behavior, the science of panic management has found important practical applications in the armed forces and emergency services of the world. Many highly publicized cases of panic occurred during massive public events. The layout of Mecca was extensively redesigned by Saudi authorities in an attempt to eliminate frequent stampedes, how it works and What To Do About It — by Bruce Tognazzini. — Professor Lee Clarke, Contexts Magazine,2002

17.
Radiation
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In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. Radiation is often categorized as either ionizing or non-ionizing depending on the energy of the radiated particles, Ionizing radiation carries more than 10 eV, which is enough to ionize atoms and molecules, and break chemical bonds. This is an important distinction due to the difference in harmfulness to living organisms. A common source of ionizing radiation is radioactive materials that emit α, β, or γ radiation, consisting of helium nuclei, electrons or positrons, gamma rays, X-rays and the higher energy range of ultraviolet light constitute the ionizing part of the electromagnetic spectrum. The lower-energy, longer-wavelength part of the spectrum including visible light, infrared light, microwaves and this type of radiation only damages cells if the intensity is high enough to cause excessive heating. Ultraviolet radiation has some features of both ionizing and non-ionizing radiation and these properties derive from ultraviolets power to alter chemical bonds, even without having quite enough energy to ionize atoms. The word radiation arises from the phenomenon of waves radiating from a source and this aspect leads to a system of measurements and physical units that are applicable to all types of radiation. This law does not apply close to a source of radiation or for focused beams. Radiation with sufficiently high energy can ionize atoms, that is to say it can knock electrons off atoms, ionization occurs when an electron is stripped from an electron shell of the atom, which leaves the atom with a net positive charge. Because living cells and, more importantly, the DNA in those cells can be damaged by this ionization, thus ionizing radiation is somewhat artificially separated from particle radiation and electromagnetic radiation, simply due to its great potential for biological damage. While an individual cell is made of trillions of atoms, only a fraction of those will be ionized at low to moderate radiation powers. If the source of the radiation is a radioactive material or a nuclear process such as fission or fusion. Particle radiation is subatomic particles accelerated to relativistic speeds by nuclear reactions, because of their momenta they are quite capable of knocking out electrons and ionizing materials, but since most have an electrical charge, they dont have the penetrating power of ionizing radiation. The exception is neutron particles, see below, there are several different kinds of these particles, but the majority are alpha particles, beta particles, neutrons, and protons. Roughly speaking, photons and particles with energies above about 10 electron volts are ionizing, particle radiation from radioactive material or cosmic rays almost invariably carries enough energy to be ionizing. The radiation is invisible and not directly detectable by human senses, as a result, in some cases, it may lead to secondary emission of visible light upon its interaction with matter, as in the case of Cherenkov radiation and radio-luminescence. Ionizing radiation has many uses in medicine, research and construction. Ultraviolet, of wavelengths from 10 nm to 125 nm, ionizes air molecules, causing it to be absorbed by air

Radiation
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Illustration of the relative abilities of three different types of ionizing radiation to penetrate solid matter. Typical alpha particles (α) are stopped by a sheet of paper, while beta particles (β) are stopped by an aluminium plate. Gamma radiation (γ) is damped when it penetrates lead. Note caveats in the text about this simplified diagram.

18.
Body mass index
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The body mass index or Quetelet index is a value derived from the mass and height of an individual. The BMI is defined as the body divided by the square of the body height. The BMI is an attempt to quantify the amount of mass in an individual. However, there is debate about where on the BMI scale the dividing lines between categories should be placed. Commonly accepted BMI ranges are underweight, under 18.5 kg/m2, normal weight,18.5 to 25, overweight,25 to 30, obese, over 30. The modern term body mass index for the ratio of body weight to squared height was coined in a paper published in the July 1972 edition of the Journal of Chronic Diseases by Ancel Keys. In this paper, Keys argued that what he termed the BMI was, BMI was explicitly cited by Keys as appropriate for population studies and inappropriate for individual evaluation. Nevertheless, due to its simplicity, it has come to be used for preliminary diagnosis. Additional metrics, such as waist circumference, can be more useful, the BMI is universally expressed in kg/m2, resulting from mass in kilograms and height in metres. If pounds and inches are used, a factor of 703 / must be applied. When the term BMI is used informally, the units are usually omitted, BMI was designed to be used as a simple means of classifying average sedentary populations, with an average body composition. Some athletes, such as linemen, have a high muscle to fat ratio. BMI is proportional to the mass and inversely proportional to the square of the height, so, if all body dimensions double, and mass scales naturally with the cube of the height, then BMI doubles instead of remaining the same. This results in people having a reported BMI that is uncharacteristically high. In comparison, the Ponderal index is based on the scaling of mass with the third power of the height. However, many people are not just scaled up short people. Nick Korevaar suggests that instead of squaring the body height or cubing the body height, carl Lavie has written that, The B. M. I. Tables are excellent for identifying obesity and body fat in large populations, a frequent use of the BMI is to assess how much an individuals body weight departs from what is normal or desirable for a persons height

Body mass index
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A graph of body mass index as a function of body mass and body height. The dashed lines represent subdivisions within a major class.

19.
Surface area
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The surface area of a solid object is a measure of the total area that the surface of the object occupies. Smooth surfaces, such as a sphere, are assigned surface area using their representation as parametric surfaces and this definition of surface area is based on methods of infinitesimal calculus and involves partial derivatives and double integration. A general definition of area was sought by Henri Lebesgue. Their work led to the development of measure theory, which studies various notions of surface area for irregular objects of any dimension. An important example is the Minkowski content of a surface, while the areas of many simple surfaces have been known since antiquity, a rigorous mathematical definition of area requires a great deal of care. This should provide a function S ↦ A which assigns a real number to a certain class of surfaces that satisfies several natural requirements. The most fundamental property of the area is its additivity. More rigorously, if a surface S is a union of many pieces S1, …, Sr which do not overlap except at their boundaries. Surface areas of polygonal shapes must agree with their geometrically defined area. Since surface area is a notion, areas of congruent surfaces must be the same and the area must depend only on the shape of the surface. This means that surface area is invariant under the group of Euclidean motions and these properties uniquely characterize surface area for a wide class of geometric surfaces called piecewise smooth. Such surfaces consist of many pieces that can be represented in the parametric form S D, r → = r →, ∈ D with a continuously differentiable function r →. The area of a piece is defined by the formula A = ∬ D | r → u × r → v | d u d v. Thus the area of SD is obtained by integrating the length of the vector r → u × r → v to the surface over the appropriate region D in the parametric uv plane. The area of the surface is then obtained by adding together the areas of the pieces. The main formula can be specialized to different classes of surfaces, giving, in particular, formulas for areas of graphs z = f and surfaces of revolution. It was demonstrated by Hermann Schwarz that already for the cylinder, various approaches to a general definition of surface area were developed in the late nineteenth and the early twentieth century by Henri Lebesgue and Hermann Minkowski. While for piecewise smooth surfaces there is a natural notion of surface area, if a surface is very irregular, or rough

20.
Volume
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Volume is the quantity of three-dimensional space enclosed by a closed surface, for example, the space that a substance or shape occupies or contains. Volume is often quantified numerically using the SI derived unit, the cubic metre, three dimensional mathematical shapes are also assigned volumes. Volumes of some simple shapes, such as regular, straight-edged, volumes of a complicated shape can be calculated by integral calculus if a formula exists for the shapes boundary. Where a variance in shape and volume occurs, such as those that exist between different human beings, these can be calculated using techniques such as the Body Volume Index. One-dimensional figures and two-dimensional shapes are assigned zero volume in the three-dimensional space, the volume of a solid can be determined by fluid displacement. Displacement of liquid can also be used to determine the volume of a gas, the combined volume of two substances is usually greater than the volume of one of the substances. However, sometimes one substance dissolves in the other and the volume is not additive. In differential geometry, volume is expressed by means of the volume form, in thermodynamics, volume is a fundamental parameter, and is a conjugate variable to pressure. Any unit of length gives a unit of volume, the volume of a cube whose sides have the given length. For example, a cubic centimetre is the volume of a cube whose sides are one centimetre in length, in the International System of Units, the standard unit of volume is the cubic metre. The metric system also includes the litre as a unit of volume, thus 1 litre =3 =1000 cubic centimetres =0.001 cubic metres, so 1 cubic metre =1000 litres. Small amounts of liquid are often measured in millilitres, where 1 millilitre =0.001 litres =1 cubic centimetre. Capacity is defined by the Oxford English Dictionary as the applied to the content of a vessel, and to liquids, grain, or the like. Capacity is not identical in meaning to volume, though closely related, Units of capacity are the SI litre and its derived units, and Imperial units such as gill, pint, gallon, and others. Units of volume are the cubes of units of length, in SI the units of volume and capacity are closely related, one litre is exactly 1 cubic decimetre, the capacity of a cube with a 10 cm side. In other systems the conversion is not trivial, the capacity of a fuel tank is rarely stated in cubic feet, for example. The density of an object is defined as the ratio of the mass to the volume, the inverse of density is specific volume which is defined as volume divided by mass. Specific volume is an important in thermodynamics where the volume of a working fluid is often an important parameter of a system being studied

21.
National Health Service
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The National Health Service is the name of the public health services of England, Scotland and Wales, and is commonly used to refer to those of Northern Ireland. They were established together as one of the social reforms following the Second World War on the founding principles of being comprehensive, universal. Today, each provides a range of health services, the vast majority of which are free for people ordinarily resident in the United Kingdom. Taken together, the four National Health Services in 2015-16 employed around 1.6 million people with a budget of £136.7 billion. For non-residents, the NHS is free at the time of use, for general practitioner, the NHS began on the Appointed Day of 5 July 1948. This put into practice Westminster legislation for England and Wales from 1946 and Scotland from 1947, when Clement Attlees Labour Party won the 1945 election he appointed Aneurin Bevan as Health Minister. Bevan then embarked upon what the historian of the NHS, Charles Webster. Three years after the founding of the NHS, Bevan resigned from the Labour government in opposition to the introduction of charges for the provision of dentures and glasses, the following year, Winston Churchills Conservative government introduced prescription charges. These charges were the first of many controversies over reforms to the NHS throughout its history, each of the UKs four nations have their own separate NHS, each with its own history. From its earliest days, the history of the NHS has shown its place in British society reflected and debated in film, TV, cartoons. However, some functions might be performed by one health service on behalf of another. There have been issues about cross-border payments, taken together, the four National Health Services in 2015-16 employed around 1.6 million people with a combined budget of £136.7 billion. In 2014 the total health sector workforce across the UK was 2,165,043 and this broke down into 1,789,586 in England,198,368 in Scotland,110,292 in Wales and 66,797 in Northern Ireland. The NHS is free at the time of use, for general practitioner and emergency treatment not including admission to hospital, people with the right to medical care in European Economic Area nations are also entitled to free treatment by using the European Health Insurance Card. Those from other countries with which the UK has reciprocal arrangements also qualify for free treatment, people not ordinarily resident in the UK are in general not entitled to free hospital treatment, with some exceptions such as refugees. People not ordinarily resident may be subject to an interview to establish their eligibility, patients who do not qualify for free treatment are asked to pay in advance, or to sign a written undertaking to pay, except for emergency treatment. The provision of treatment to non-UK-residents, formerly interpreted liberally, has been increasingly restricted. As of 2016 the surcharge was £200 per year, with exemptions and reductions in some cases, the systems are 98. 8% funded from general taxation and National Insurance contributions, plus small amounts from patient charges for some services

National Health Service
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Leaflet concerning the launch of the NHS in England and Wales.
National Health Service
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Aneurin Bevan, who spearheaded the establishment of the National Health Service

22.
Hot water bottle
–
A hot water bottle is a container filled with hot water and sealed with a stopper, used to provide warmth, typically while in bed, but also for the application of heat to a specific part of the body. Containers for warmth in bed were in use as early as the 16th century, the earliest versions contained hot coals from the dying embers of the fire, and these bed warmers were used to warm the bed before getting into it. Containers using hot water were also used, with the advantage that they could remain in the bed with the sleeper. Prior to the invention of rubber that could withstand sufficient heat, to prevent burning, the metal hot water flasks were wrapped in a soft cloth bag. India rubber hot water bottles were in use in Britain at least by 1875, modern conventional hot water bottles were patented in 1903 and are manufactured in natural rubber or PVC, to a design patented by the Croatian inventor Eduard Penkala. They are now covered in fabric, sometimes with a novelty design. By the late 20th century, the use of hot water bottles had markedly declined around most of the world, not only were homes better heated, but newer items such as electric blankets were competing with hot water bottles as a source of night-time heat. However the hot water remains a popular alternative in Australia, Ireland, United Kingdom, developing countries. For example, it is used in Chile, where it is called a guatero. There has been a recent surge in popularity in Japan where it is seen as an ecologically friendly, some newer products function like the older bottles, but use a polymer gel or wax in a heat pad. The pads can be heated in an oven, and they are marketed as safer than liquid-filled bottles or electrically-heated devices. Some newer bottles now use a silicone-based material instead of rubber, which resists very hot water better, although the stopper size in Ireland and the UK has been largely standard for many decades, the newer bottles use a wider mouth which is easier to fill. Hot water bottles are meant to very hot fluids and also supposed to be in contact with human skin. More generally, it is crucial to certify and assure that hot water bottles, whether manufactured, for instance, the United Kingdom defined British Standards for hot water bottles to regulate their manufacture and sale as well as to ensure their compliance with all safety standards. Most regulations applied to a country are generally harmonized in order to be applied and applicable in a larger area, there have been problems with premature failure of rubber hot water bottles due to faulty manufacture. The rubber may fail strength or fitness tests, or become brittle if manufacturing is not controlled closely, natural rubber filled with calcium carbonate is the most common material used, but is susceptible to oxidation and polymer degradation at the high temperatures used in shaping the product. Boiling water is not recommended for use in hot water bottles and this is due to risks of the rubber being degraded from high-temperature water, and the risk of injury in case of breakage. Alfred, the hot water bottle, is a character from Johnson and Friends

Hot water bottle
–
A metal hot water bottle from 1925
Hot water bottle
–
Two modern hot water bottles shown with their stoppers
Hot water bottle
–
An electric hot-water bottle

23.
Chest
–
The thorax or chest is a part of the anatomy of humans and various other animals located between the neck and the abdomen. The thorax includes the thoracic cavity and the thoracic wall and it contains organs including the heart, lungs, and thymus gland, as well as muscles and various other internal structures. Many diseases may affect the chest, and one of the most common symptoms is chest pain, in humans and other hominids, the thorax is the chest region of the body between the neck and the abdomen, along with its internal organs and other contents. It is mostly protected and supported by the rib cage, spine, arteries and veins are also contained –, bones. The area exposed by open-necked shirts, the V of the chest is sometimes the location of a skin disease polymorphous light eruption. In the human body, the region of the thorax between the neck and diaphragm in the front of the body is called the chest, the corresponding area in an animal can also be referred to as the chest. The shape of the chest does not correspond to part of the thoracic skeleton that encloses the heart. All the breadth of the shoulders is due to the girdle, and contains the axillae. Level with this line the second ribs join the sternum, at the lower part of the sternum, where the seventh or last true ribs join it, the ensiform cartilage begins, and above this there is often a depression known as the pit of the stomach. The bones of the thorax, called the thoracic skeleton is a component of the axial skeleton and it consists of the ribs and sternum. The ribs of the thorax are numbered in ascending order from 1-12. 11 &12 are known as floating ribs because they have no anterior attachment point in particular the cartilage attached to the sternum, as 1-7 are, whereas ribs 8-10 are termed false ribs as their costal cartilage articulates with the rib aboves costal cartilage. The anatomy of the chest can also be described through the use of anatomical landmarks, the female nipple is surrounded for half an inch by a more or less pigmented disc, the areola. The apex of a heart is in the fifth left intercostal space. Different types of diseases or conditions that affect the chest include pleurisy, flail chest, atelectasis, and these conditions can be hereditary or caused by birth defects or trauma. Any condition that lowers the ability to breathe deeply or to cough is considered a chest disease or condition. Injury to the chest results in up to ¼ of all due to trauma in the United States. The major pathophysiologies encountered in blunt chest trauma involve derangements in the flow of air, blood, sepsis due to leakage of alimentary tract contents, as in esophageal perforations, also must be considered. Blunt trauma commonly results in chest wall injuries, the pain associated with these injuries can make breathing difficult, and this may compromise ventilation

Chest
–
X-ray image of the chest showing the internal anatomy of the rib cage, lungs and heart as well as the inferior thoracic border–made up of the diaphragm.
Chest
–
Thorax. Anterior view.
Chest

24.
Cardiac output
–
Cardiac output, is a term used in cardiac physiology that describes the volume of blood being pumped by the heart, in particular by a left or right ventricle, per unit time. CO values can be represented using many physical units, such as dm3/min and L/min, because cardiac output is related to the quantity of blood delivered to various parts of the body, it is an important indicator of how efficiently the heart can meet the demands of the body. For instance, infections are correlated with high CO and heart failure with low CO, along with stroke volume, cardiac output is a global blood flow parameter of interest in hæmodynamics – the study of the flow of blood under external forces. The factors affecting stroke volume and heart rate also affect cardiac output, the figure to the right illustrates this dependency and lists some of these factors. A detailed hierarchical illustration is provided in a subsequent figure, there are many methods of measuring CO, both invasively and non-invasively, each with its own advantages and drawbacks. No standard or reference measurement against which all of these methods can be compared exists, the function of the heart is to drive blood through the circulatory system in a cycle that delivers oxygen, nutrients and chemicals to the bodys cells and removes cellular waste. This is detailed in equation below, there are a number of clinical methods to measure cardiac output, ranging from direct intracardiac catheterisation to non-invasive measurement of the arterial pulse. Each method has advantages and drawbacks, relative comparison is limited by the absence of a widely accepted gold standard measurement. Cardiac output can also be affected significantly by the phase of respiration – intra-thoracic pressure changes influence diastolic filling and this is especially important during mechanical ventilation, in which cardiac output can vary by up to 50% across a single respiratory cycle. Cardiac output should therefore be measured at evenly spaced points over a cycle or averaged over several cycles. Invasive methods are accepted, but there is increasing evidence that these methods are neither accurate nor effective in guiding therapy. Consequently, the focus on development of methods is growing. This method uses ultrasound and the Doppler effect to measure cardiac output, the blood velocity through the heart causes a Doppler shift in the frequency of the returning ultrasound waves. Echocardiography is a method of quantifying cardiac output using ultrasound. Two-dimensional ultrasound and Doppler measurements are used together to calculate cardiac output, the result is then multiplied by the heart rate to obtain cardiac output. Although used in medicine, it has a wide test-retest variability. It is said to require training and skill, but the exact steps needed to achieve clinically adequate precision have never been disclosed. 2D measurement of the valve diameter is one source of noise, others are beat-to-beat variation in stroke volume

25.
Cold-induced diuresis
–
Diuresis is increased urination and the physiologic process that produces such an increase. It involves extra urine production in the kidneys as part of the bodys maintenance of fluid balance. In healthy people, the drinking of water produces mild diuresis to maintain the body water balance. Many people with problems such as heart failure and kidney failure need diuretic medications to help their kidneys deal with the fluid overload of edema. These drugs help the body rid itself of water via the extra urine. Sometimes a connotative difference is felt between diuresis in the sense of appropriate increase and polyuria in the sense of inappropriate increase, however, sometimes the words are simply synonymous. Osmotic diuresis is the increase of urination caused by the presence of certain substances in the small tubes of the kidneys. The excretion occurs when substances such as enter the kidney tubules. The substances cause an increase in the pressure within the tubule, causing retention of water within the lumen. The same effect can be seen in such as mannitol. Substances in the circulation can also increase the amount of circulating fluid by increasing the osmolarity of the blood and this has the effect of pulling water from the interstitial space, making more water available in the blood and causing the kidney to compensate by removing it as urine. As blood pressure increases, the kidney removes the excess fluid as urine, sodium, chloride, potassium are excreted in Osmotic diuresis, originating from Diabetes Mellitus. Osmotic diuresis results in dehydration from polyuria and the classic polydipsia associated with DM, forced diuresis may enhance the excretion of certain drugs in urine and is used to treat drug overdose or poisoning of these drugs and hemorrhagic cystitis. Most of the drugs are weak acids or weak bases. When urine is made alkaline, elimination of drugs in the urine is increased. The converse applies for alkaline drugs, for acidic drugs, urine pH should be above the pK value of that drug, and converse for the basic drugs. It is because the ionization of acidic drug is increased in alkaline urine and this method is ineffective for drugs which are strongly protein bound or which have a large apparent volume of distribution. For forced alkaline diuresis, sodium bicarbonate is added to the fluid to make blood and, in turn

26.
Avalanche
–
An avalanche is a rapid flow of snow down a sloping surface. Avalanches are typically triggered in a zone from a mechanical failure in the snowpack when the forces on the snow exceed its strength. After initiation, avalanches usually accelerate rapidly and grow in mass, if the avalanche moves fast enough some of the snow may mix with the air forming a powder snow avalanche, which is a type of gravity current. Slides of rocks or debris, behaving in a way to snow, are also referred to as avalanches. The remainder of this article refers to snow avalanches, the load on the snowpack may be only due to gravity, in which case failure may result either from weakening in the snowpack or increased load due to precipitation. Avalanches that occur in this way are known as spontaneous avalanches, Avalanches can also be triggered by other loads such as skiers, snowmobilers, animals or explosives. Seismic activity may trigger the failure in the snowpack and avalanches. A popular myth is that avalanches can be triggered by loud noise or shouting, Avalanches are not rare or random events and are endemic to any mountain range that accumulates a standing snowpack. Avalanches are most common during winter or spring but glacier movements may cause ice, there is no universally accepted classification of avalanches—different classifications are useful for different purposes. Avalanches can be described by their size, their potential, their initiation mechanism, their composition. Most avalanches occur spontaneously during storms under increased load due to snowfall, the second largest cause of natural avalanches is metamorphic changes in the snowpack such as melting due to solar radiation. Other natural causes include rain, earthquakes, rockfall and icefall, artificial triggers of avalanches include skiers, snowmobiles, and controlled explosive work. Avalanche initiation can start at a point with only an amount of snow moving initially. A snowpack will fail when the load exceeds the strength, the load is straightforward, it is the weight of the snow. However, the strength of the snowpack is much more difficult to determine and is extremely heterogenous and it varies in detail with properties of the snow grains, size, density, morphology, temperature, water content, and the properties of the bonds between the grains. These properties may all metamorphose in time according to the humidity, water vapour flux, temperature. The top of the snowpack is also influenced by incoming radiation. One of the aims of research is to develop and validate computer models that can describe the evolution of the seasonal snowpack over time

Avalanche
–
The toe of an avalanche in Alaska 's Kenai Fjords.
Avalanche
–
A powder snow avalanche in the Himalayas near Mount Everest.
Avalanche
–
A crown fracture from a slab avalanche near the Neve Glacier in the North Cascades mountains. Extensive fracture propagation is evident.
Avalanche
–
Loose snow avalanches (far left) and slab avalanches (near center) near Mount Shuksan in the North Cascades mountains. Fracture propagation is relatively limited.

27.
Metabolism
–
Metabolism is the set of life-sustaining chemical transformations within the cells of living organisms. These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, usually, breaking down releases energy and building up consumes energy. The chemical reactions of metabolism are organized into metabolic pathways, in one chemical is transformed through a series of steps into another chemical. Enzymes act as catalysts that allow the reactions to proceed more rapidly, enzymes also allow the regulation of metabolic pathways in response to changes in the cells environment or to signals from other cells. The metabolic system of a particular organism determines which substances it will find nutritious, for example, some prokaryotes use hydrogen sulfide as a nutrient, yet this gas is poisonous to animals. The speed of metabolism, the rate, influences how much food an organism will require. A striking feature of metabolism is the similarity of the metabolic pathways. These striking similarities in metabolic pathways are likely due to their appearance in evolutionary history. Most of the structures that make up animals, plants and microbes are made from three classes of molecule, amino acids, carbohydrates and lipids. These biochemicals can be joined together to make such as DNA and proteins. Proteins are made of amino acids arranged in a linear chain joined together by peptide bonds, many proteins are enzymes that catalyze the chemical reactions in metabolism. Other proteins have structural or mechanical functions, such as those that form the cytoskeleton, Proteins are also important in cell signaling, immune responses, cell adhesion, active transport across membranes, and the cell cycle. Lipids are the most diverse group of biochemicals and their main structural uses are as part of biological membranes both internal and external, such as the cell membrane, or as a source of energy. Lipids are usually defined as hydrophobic or amphipathic biological molecules but will dissolve in organic solvents such as benzene or chloroform, the fats are a large group of compounds that contain fatty acids and glycerol, a glycerol molecule attached to three fatty acid esters is called a triacylglyceride. Several variations on this structure exist, including alternate backbones such as sphingosine in the sphingolipids. Steroids such as cholesterol are another class of lipids. Carbohydrates are aldehydes or ketones, with hydroxyl groups attached. Carbohydrates are the most abundant biological molecules, and fill numerous roles, such as the storage and transport of energy, the basic carbohydrate units are called monosaccharides and include galactose, fructose, and most importantly glucose

Metabolism
–
Plant cells (bounded by purple walls) filled with chloroplasts (green), which are the site of photosynthesis
Metabolism
–
Structure of adenosine triphosphate (ATP), a central intermediate in energy metabolism
Metabolism
–
Santorio Santorio in his steelyard balance, from Ars de statica medicina, first published 1614
Metabolism
–
Diving medicine:

28.
Napoleon
–
Napoleon Bonaparte was a French military and political leader who rose to prominence during the French Revolution and led several successful campaigns during the French Revolutionary Wars. As Napoleon I, he was Emperor of the French from 1804 until 1814, Napoleon dominated European and global affairs for more than a decade while leading France against a series of coalitions in the Napoleonic Wars. He won most of these wars and the vast majority of his battles, one of the greatest commanders in history, his wars and campaigns are studied at military schools worldwide. Napoleons political and cultural legacy has ensured his status as one of the most celebrated and he was born Napoleone di Buonaparte in Corsica to a relatively modest family from the minor nobility. When the Revolution broke out in 1789, Napoleon was serving as an officer in the French army. Seizing the new opportunities presented by the Revolution, he rose through the ranks of the military. The Directory eventually gave him command of the Army of Italy after he suppressed a revolt against the government from royalist insurgents, in 1798, he led a military expedition to Egypt that served as a springboard to political power. He engineered a coup in November 1799 and became First Consul of the Republic and his ambition and public approval inspired him to go further, and in 1804 he became the first Emperor of the French. Intractable differences with the British meant that the French were facing a Third Coalition by 1805, in 1806, the Fourth Coalition took up arms against him because Prussia became worried about growing French influence on the continent. Napoleon quickly defeated Prussia at the battles of Jena and Auerstedt, then marched the Grand Army deep into Eastern Europe, France then forced the defeated nations of the Fourth Coalition to sign the Treaties of Tilsit in July 1807, bringing an uneasy peace to the continent. Tilsit signified the high watermark of the French Empire, hoping to extend the Continental System and choke off British trade with the European mainland, Napoleon invaded Iberia and declared his brother Joseph the King of Spain in 1808. The Spanish and the Portuguese revolted with British support, the Peninsular War lasted six years, featured extensive guerrilla warfare, and ended in victory for the Allies. The Continental System caused recurring diplomatic conflicts between France and its client states, especially Russia, unwilling to bear the economic consequences of reduced trade, the Russians routinely violated the Continental System and enticed Napoleon into another war. The French launched an invasion of Russia in the summer of 1812. The resulting campaign witnessed the collapse of the Grand Army, the destruction of Russian cities, in 1813, Prussia and Austria joined Russian forces in a Sixth Coalition against France. A lengthy military campaign culminated in a large Allied army defeating Napoleon at the Battle of Leipzig in October 1813, the Allies then invaded France and captured Paris in the spring of 1814, forcing Napoleon to abdicate in April. He was exiled to the island of Elba near Rome and the Bourbons were restored to power, however, Napoleon escaped from Elba in February 1815 and took control of France once again. The Allies responded by forming a Seventh Coalition, which defeated Napoleon at the Battle of Waterloo in June, the British exiled him to the remote island of Saint Helena in the South Atlantic, where he died six years later at the age of 51

29.
J. M. W. Turner
–
Joseph Mallord William Turner, RA was an English Romanticist landscape painter. Turner was considered a figure in his day, but is now regarded as the artist who elevated landscape painting to an eminence rivalling history painting. Although renowned for his oil paintings, Turner is also one of the greatest masters of British watercolour landscape painting and he is commonly known as the painter of light. Joseph Mallord William Turner was baptised on 14 May 1775, and it is generally believed he was born between late April and early May. Turner himself claimed he was born on 23 April, but there is no proof and he was born in Maiden Lane, Covent Garden, in London, England. His father, William Turner, was a barber and wig maker and his mother, Mary Marshall, came from a family of butchers. A younger sister, Mary Ann, was born in September 1778, the earliest known artistic exercise by Turner is from this period—a series of simple colourings of engraved plates from Henry Boswells Picturesque View of the Antiquities of England and Wales. Around 1786, Turner was sent to Margate on the north-east Kent coast, here he produced a series of drawings of the town and surrounding area foreshadowing his later work. Turner returned to Margate many times in later life, by this time, Turners drawings were being exhibited in his fathers shop window and sold for a few shillings. His father boasted to the artist Thomas Stothard that, My son, in 1789, Turner again stayed with his uncle who had retired to Sunningwell in Berkshire. A whole sketchbook of work from time in Berkshire survives as well as a watercolour of Oxford. The use of sketches on location, as the foundation for later finished paintings. By the end of 1789, he had begun to study under the topographical draughtsman Thomas Malton. Turner learned from him the tricks of the trade, copying and colouring outline prints of British castles. He would later call Malton My real master, topography was a thriving industry by which a young artist could pay for his studies. In the same year of 1789 he entered the Royal Academy of Art schools, when he was 14 years old, Sir Joshua Reynolds, president of the Royal Academy, chaired the panel that admitted him. At first Turner showed a keen interest in architecture, but was advised by the architect Thomas Hardwick to continue painting and his first watercolour painting A View of the Archbishops Palace, Lambeth was accepted for the Royal Academy summer exhibition of 1790 when Turner was 15. As a probationer in the academy, he was drawing from plaster casts of antique sculptures

J. M. W. Turner
–
Self-portrait, oil on canvas, circa 1799
J. M. W. Turner
–
Drawing of St John's Church, Margate by Turner from around 1786, when he would have been 11 or 12 years old. The ambitious but unsure drawing shows an early struggle with perspective, which can be contrasted with his later work
J. M. W. Turner
–
A View of the Archbishop's Palace, Lambeth – this watercolour was Turner's first to be accepted for the Royal Academy's annual exhibition in April 1790, the month he turned 15. The image is a technical presentation of Turner's strong grasp of the elements of perspective with several buildings at sharp angles to each other, demonstrating Turner's thorough mastery of Thomas Malton's topographical style.
J. M. W. Turner
–
Fishermen at Sea exhibited in 1796 was the first oil painting exhibited by Turner at the Royal Academy

30.
Hannibal
–
Hannibal Barca, was a Carthaginian general, considered one of the greatest military commanders in history. His father Hamilcar Barca was the leading Carthaginian commander during the First Punic War and his younger brothers were Mago and Hasdrubal, and he was brother-in-law to Hasdrubal the Fair. One of his most famous achievements was at the outbreak of the Second Punic War, when he marched an army which included war elephants from Iberia over the Pyrenees, Hannibal occupied much of Italy for 15 years but was unable to march on Rome. An enemy counter-invasion of North Africa forced him to return to Carthage, after the war, Hannibal successfully ran for the office of sufet. During this time, he lived at the Seleucid court, where he acted as advisor to Antiochus III the Great in his war against Rome. Antiochus met defeat at the Battle of Magnesia and was forced to accept Romes terms and his flight ended in the court of Bithynia, where he achieved an outstanding naval victory against a fleet from Pergamon. He was afterwards betrayed to the Romans and committed suicide by poisoning himself, military historian Theodore Ayrault Dodge called Hannibal the father of strategy, because his greatest enemy, Rome, came to adopt elements of his military tactics in its own strategic arsenal. This praise has earned him a reputation in the modern world. The English form of the name is derived from the Latin, Greek historians rendered the name as Anníbas Bárkas. Hannibals name was recorded in Carthaginian sources as ḤNBʻL and its precise vocalization remains a matter of debate. Suggested readings include Ḥannibaʻl or Ḥannibaʻal, meaning grace of Baʻal, Baal is gracious, or Baal has been gracious, or Ḥannobaʻal, Barca was the surname of his aristocratic family, meaning shining or lightning. It is thus equivalent to the Arabic name Barq or the Hebrew name Barak or the ancient Greek epithet keraunos, in English, his clan are sometimes collectively known as the Barcids. As with Greek and Roman practice, patronymics were a part of Carthaginian nomenclature. Hannibal was one of the sons of Hamilcar Barca, a Carthaginian leader and he was born in what is present day Tunisia. He had several sisters and two brothers, Hasdrubal and Mago and his brothers-in-law were Hasdrubal the Fair and the Numidian king Naravas. He was still a child when his sisters married, and his brothers-in-law were close associates during his fathers struggles in the Mercenary War, in light of Hamilcar Barcas cognomen, historians refer to Hamilcars family as the Barcids. However, there is debate as to whether the cognomen Barca was applied to Hamilcar alone or was hereditary within his family, if the latter, then Hannibal and his brothers also bore the name Barca. After Carthages defeat in the First Punic War, Hamilcar set out to improve his familys, with that in mind and supported by Gades, Hamilcar began the subjugation of the tribes of the Iberian Peninsula

Hannibal
–
A marble bust, reputedly of Hannibal, originally found at the ancient city-state of Capua in Italy (some historians are uncertain of the authenticity of the portrait).
Hannibal
–
Hannibal and his men crossing the Alps.
Hannibal
–
Hannibal counting the signet rings of Roman nobles killed during the battle, statue by Sébastien Slodtz, 1704, Louvre.
Hannibal
–
Scipio Africanus

31.
Before Christ
–
The terms anno Domini and before Christ are used to label or number years in the Julian and Gregorian calendars. The term anno Domini is Medieval Latin and means in the year of the Lord, There is no year zero in this scheme, so the year AD1 immediately follows the year 1 BC. This dating system was devised in 525 by Dionysius Exiguus of Scythia Minor, the Gregorian calendar is the most widely used calendar in the world today. Traditionally, English followed Latin usage by placing the AD abbreviation before the year number, however, BC is placed after the year number, which also preserves syntactic order. The abbreviation is widely used after the number of a century or millennium. Because BC is the English abbreviation for Before Christ, it is sometimes concluded that AD means After Death. However, this would mean that the approximate 33 years commonly associated with the life of Jesus would not be included in either of the BC, astronomical year numbering and ISO8601 avoid words or abbreviations related to Christianity, but use the same numbers for AD years. The Anno Domini dating system was devised in 525 by Dionysius Exiguus to enumerate the years in his Easter table. His system was to replace the Diocletian era that had used in an old Easter table because he did not wish to continue the memory of a tyrant who persecuted Christians. The last year of the old table, Diocletian 247, was followed by the first year of his table. Thus Dionysius implied that Jesus Incarnation occurred 525 years earlier, without stating the year during which his birth or conception occurred. Blackburn & Holford-Strevens briefly present arguments for 2 BC,1 BC, There were inaccuracies in the list of consuls There were confused summations of emperors regnal years It is not known how Dionysius established the year of Jesuss birth. It is convenient to initiate a calendar not from the day of an event. For example, the Islamic calendar begins not from the date of the Hegira, at the time, it was believed by some that the Resurrection and end of the world would occur 500 years after the birth of Jesus. The old Anno Mundi calendar theoretically commenced with the creation of the based on information in the Old Testament. It was believed that, based on the Anno Mundi calendar, Anno Mundi 6000 was thus equated with the resurrection and the end of the world but this date had already passed in the time of Dionysius. The Anglo-Saxon historian the Venerable Bede, who was familiar with the work of Dionysius Exiguus, used Anno Domini dating in his Ecclesiastical History of the English People, completed in 731. e. On the continent of Europe, Anno Domini was introduced as the era of choice of the Carolingian Renaissance by the English cleric and scholar Alcuin in the late eighth century

32.
French invasion of Russia
–
Napoleon hoped to compel Tsar Alexander I of Russia to cease trading with British merchants through proxies in an effort to pressure the United Kingdom to sue for peace. The official political aim of the campaign was to liberate Poland from the threat of Russia, Napoleon named the campaign the Second Polish War to gain favor with the Poles and provide a political pretext for his actions. The Grande Armée was a large force, numbering 680,000 soldiers. Napoleon hoped the battle would mean an end of the march into Russia, plans Napoleon had made to quarter at Smolensk were abandoned, and he pressed his army on after the Russians. As the Russian army fell back, Cossacks were given the task of burning villages, towns and this was intended to deny the invaders the option of living off the land. The actions forced the French to rely on a system that was incapable of feeding the large army in the field. Starvation and privation compelled French soldiers to leave their camps at night in search of food and these men were frequently confronted by parties of Cossacks, who captured or killed them. The Russian army retreated into Russia for almost three months, the continual retreat and the loss of lands to the French upset the Russian nobility. They pressured Alexander I to relieve the commander of the Russian army, Alexander I complied, appointing an old veteran, Prince Mikhail Kutuzov, to take over command of the army. However, for two more weeks Kutuzov continued to retreat as his predecessor had done, on 7 September, the French caught up with the Russian army which had dug itself in on hillsides before a small town called Borodino, seventy miles west of Moscow. The battle that followed was the bloodiest single-day action of the Napoleonic Wars until that point, involving more than 250,000 soldiers, the French gained a tactical victory, but at the cost of 49 general officers and thousands of men. The Russian army was able to extricate itself and withdrew the following day, Napoleon entered Moscow a week later. In another turn of events the French found puzzling, there was no delegation to meet the Emperor, the Russians had evacuated the city, and the citys governor, Count Fyodor Rostopchin, ordered several strategic points in Moscow set ablaze. Napoleons hopes had been set upon an end to his campaign. The loss of Moscow did not compel Alexander I to sue for peace, Napoleon stayed on in Moscow looking to negotiate a peace, his hopes fed in part by a disinformation campaign informing the Emperor of supposed discontent and fading morale in the Russian camp. After staying a month Napoleon moved his army out southwest toward Kaluga, the French advance toward Kaluga was checked by a Russian corps. Napoleon tried once more to engage the Russian army for an action at the Battle of Maloyaroslavets. Despite holding a position, the Russians retreated following a sharp engagement

33.
Battle of Stalingrad
–
Marked by fierce close quarters combat and direct assaults on civilians by air raids, it is often regarded as one of the single largest and bloodiest battles in the history of warfare. German forces never regained the initiative in the East and withdrew a vast military force from the West to replace their losses, the German offensive to capture Stalingrad began in August 1942, using the German 6th Army and elements of the 4th Panzer Army. The attack was supported by intensive Luftwaffe bombing that reduced much of the city to rubble, the fighting degenerated into house-to-house fighting, and both sides poured reinforcements into the city. By mid-November 1942, the Germans had pushed the Soviet defenders back at great cost into narrow zones along the west bank of the Volga River. On 19 November 1942, the Red Army launched Operation Uranus, the Axis forces on the flanks were overrun and the 6th Army was cut off and surrounded in the Stalingrad area. Adolf Hitler ordered that the stay in Stalingrad and make no attempt to break out, instead, attempts were made to supply the army by air. Heavy fighting continued for two months. By the beginning of February 1943, the Axis forces in Stalingrad had exhausted their ammunition, the remaining units of the 6th Army surrendered. The battle lasted five months, one week, and three days, elsewhere, the war had been progressing well, the U-boat offensive in the Atlantic had been very successful and Rommel had just captured Tobruk. In the east, they had stabilized their front in a running from Leningrad in the north to Rostov in the south. There were a number of salients, but these were not particularly threatening, neither Army Group North nor Army Group South had been particularly hard pressed over the winter. Stalin was expecting the main thrust of the German summer attacks to be directed against Moscow again, with the initial operations being very successful, the Germans decided that their summer campaign in 1942 would be directed at the southern parts of the Soviet Union. The initial objectives in the region around Stalingrad were the destruction of the capacity of the city. The river was a key route from the Caucasus and the Caspian Sea to central Russia and its capture would disrupt commercial river traffic. The Germans cut the pipeline from the oilfields when they captured Rostov on 23 July, the capture of Stalingrad would make the delivery of Lend Lease supplies via the Persian Corridor much more difficult. On 23 July 1942, Hitler personally rewrote the operational objectives for the 1942 campaign, both sides began to attach propaganda value to the city based on it bearing the name of the leader of the Soviet Union. The expansion of objectives was a significant factor in Germanys failure at Stalingrad, caused by German overconfidence, the Soviets realized that they were under tremendous constraints of time and resources and ordered that anyone strong enough to hold a rifle be sent to fight. If I do not get the oil of Maikop and Grozny then I must finish this war, Army Group South was selected for a sprint forward through the southern Russian steppes into the Caucasus to capture the vital Soviet oil fields there

Battle of Stalingrad
–
Soviet soldier waving the Red Banner over the central plaza of Stalingrad in 1943.
Battle of Stalingrad
–
Infantry and a supporting StuG III assault gun advance towards the city center.
Battle of Stalingrad
–
October 1942: German officer with a Russian PPSh-41submachine gun in Barrikady factory rubble. Many German soldiers took up Russian weapons when found, as they were more effective than their own in close quarter combat.
Battle of Stalingrad
–
German soldiers on their way in Stalingrad

34.
MS Estonia
–
MS Estonia, previously Viking Sally, Silja Star, and Wasa King, was a cruise ferry built in 1979/80 at the German shipyard Meyer Werft in Papenburg. The ship sank in 1994 in the Baltic Sea in one of the worst maritime disasters of the 20th century and it is, after the Titanic, the second-deadliest European shipwreck disaster to have occurred in peacetime and 852 lives were lost. The ship was ordered from Meyer Werft by a Norwegian shipping company led by Parley Augustsen with intended traffic between Norway and Germany. At the last moment, the company withdrew their order and the contract went to Rederi Ab Sally, originally the ship was conceived as a sister ship to Diana II, built in 1979 by the same shipyard for Rederi AB Slite, the third partner in Viking Line. Meyer Werft had constructed a number of ships for various Viking Line partner companies during the 1970s. Worth noting is the new ships bow construction, which consisted of an upwards-opening visor, an identical bow construction had also been used in Diana II. On 29 June 1980 Viking Sally was delivered to Rederi Ab Sally and she was the largest ship to serve on that route at the time. In 1985 she was rebuilt with a duck tail. Rederi Ab Sally had been experiencing financial difficulties for most of the 1980s, in late 1987, Effoa and Johnson Line, the owners of Viking Lines main rivals Silja Line, bought Sally. As a result of this, SF Line and Rederi AB Slite forced Sally to withdraw from Viking Line, Viking Sally was chartered to Rederi AB Slite to continue on her current traffic for the next three years. When her charter ended in April 1990, Viking Sally had a change of service. She was painted in Silja Lines colours, renamed Silja Star and placed on the route that she had plied for Viking Line. Also in 1990 Effoa, Johnson Line and Rederi Ab Sally merged into EffJohn, the following spring Silja Star began her service with Wasa Line, another company owned by EffJohn. Her name was changed to Wasa King and she served on routes connecting Vaasa, Finland to Umeå and it has been reported that the Wasa King was widely considered to be the best behaving ship in rough weather to have sailed from Vaasa. The actual ownership of the ship was rather complex, in order for Nordstöm & Thulin to get a loan to buy the ship, as a result, the ship was actually registered in both Cyprus and Estonia. As the largest Estonian-owned ship of the time, the Estonia symbolized the independence that Estonia regained after the collapse of the Soviet Union. The Estonia disaster occurred on Wednesday,28 September 1994, between about 00,55 and 01,50 as the ship was crossing the Baltic Sea, en route from Tallinn, Estonia, Estonia was on a scheduled crossing with departure at 19,00 on 27 September. She had been expected in Stockholm the next morning at about 09,30 and she was carrying 989 people,803 passengers and 186 crew

35.
Nazi human experimentation
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Chief target populations included Romani, Sinti, ethnic Poles, Soviet POWs, disabled Germans, and most prominently of all, Jews from across Europe. Nazi Physicians and their assistants forced prisoners into participating, they did not willingly volunteer, typically, the experiments resulted in death, trauma, disfigurement or permanent disability, and as such are considered examples of medical torture. Aribert Heim conducted similar medical experiments at Mauthausen, Carl Værnet is known to have conducted experiments on homosexual prisoners in attempts to cure homosexuality. After the war, these crimes were tried at what became known as the Doctors Trial, the Nazi physicians in the Doctors trial argued that military necessity justified their torturous experiments, and compared their victims to collateral damage from Allied bombings. But this defense, which was in any case rejected by the Tribunal, cannot apply to the experiments of Josef Mengele. The central leader of the experiments was Josef Mengele, who from 1943 to 1944 performed experiments on nearly 1,500 sets of imprisoned twins at Auschwitz, about 200 people survived these studies. Sections of bones, muscles, and nerves were removed from the subjects without use of anesthesia, as a result of these operations, many victims suffered intense agony, mutilation, and permanent disability. Above him was a hammer that every few seconds came down upon his head. The boy was driven insane from the torture, in 1941, the Luftwaffe conducted experiments with the intent of discovering means to prevent and treat hypothermia. There were 360 to 400 experiments and 280 to 300 victims indicating some victims suffered more than one experiment, another study placed prisoners naked in the open air for several hours with temperatures as low as −6 °C. Besides studying the effects of cold exposure, the experimenters also assessed different methods of rewarming survivors. One assistant later testified that some victims were thrown into boiling water for rewarming, many experiments were conducted on captured Russian troops, the Nazis wondered whether their genetics gave them superior resistance to cold. The principal locales were Dachau and Auschwitz, approximately 100 people are reported to have died as a result of these experiments. From about February 1942 to about April 1945, experiments were conducted at the Dachau concentration camp in order to investigate immunization for treatment of malaria, healthy inmates were infected by mosquitoes or by injections of extracts of the mucous glands of female mosquitoes. After contracting the disease, the subjects were treated with drugs to test their relative efficiency. Over 1,200 people were used in experiments and more than half died as a result. Test subjects were exposed to mustard gas and other vesicants which inflicted severe chemical burns. The victims wounds were then tested to find the most effective treatment for the gas burns

36.
Tardigrade
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Tardigrades are water-dwelling, eight-legged, segmented micro-animals. They were first discovered by the German zoologist Johann August Ephraim Goeze in 1773, the name Tardigrada was given three years later by the Italian biologist Lazzaro Spallanzani. They have been found everywhere from mountaintops to the deep sea, Tardigrades are one of the most resilient animals known, they can survive extreme conditions that would be rapidly fatal to nearly all other known life forms. They can go without food or water for more than 30 years, drying out to the point where they are 3% or less water, only to rehydrate, forage and they are not considered extremophilic because they are not adapted to exploit these conditions. Usually, tardigrades are about 0.5 mm long when they are fully grown and they are short and plump with four pairs of legs, each with four to eight claws also known as disks. Tardigrades are prevalent in mosses and lichens and feed on plant cells, algae, when collected, they may be viewed under a very low-power microscope, making them accessible to students and amateur scientists. Tardigrades form the phylum Tardigrada, part of the superphylum Ecdysozoa and it is an ancient group, with fossils dating from 530 million years ago, in the Cambrian period. About 1,150 species of tardigrades have been described, Tardigrades can be found throughout the world, from the Himalayas, to the deep sea and from the polar regions to the equator. Johann August Ephraim Goeze originally named the tardigrade kleiner Wasserbär, meaning little water bear in German, the name Tardigrada means slow walker and was given by Lazzaro Spallanzani in 1776. The name water bear comes from the way they walk, reminiscent of a bears gait, the biggest adults may reach a body length of 1.5 mm, the smallest below 0.1 mm. Newly hatched tardigrades may be smaller than 0.05 mm, the most convenient place to find tardigrades is on lichens and mosses. Other environments are dunes, beaches, soil, and marine or freshwater sediments, Tardigrades, in the case of Echiniscoides wyethi, may be found on barnacles. Often, tardigrades can be found by soaking a piece of moss in water, Tardigrades have barrel-shaped bodies with four pairs of stubby legs. Most range from 0.3 to 0.5 mm in length, the body consists of a head, three body segments with a pair of legs each, and a caudal segment with a fourth pair of legs. The legs are without joints, while the feet have four to eight claws each, the cuticle contains chitin and protein and is moulted periodically. Tardigrades are eutelic, meaning all adult tardigrades of the species have the same number of cells. Some species have as many as 40,000 cells in each adult, the body cavity consists of a haemocoel, but the only place where a true coelom can be found is around the gonad. No respiratory organs are found, with gas exchange able to occur across the whole of the body, some tardigrades have three tubular glands associated with the rectum, these may be excretory organs similar to the Malpighian tubules of arthropods, although the details remain unclear

37.
Sugar
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Sugar is the generic name for sweet, soluble carbohydrates, many of which are used in food. There are various types of derived from different sources. Simple sugars are called monosaccharides and include glucose, fructose, the table sugar or granulated sugar most customarily used as food is sucrose, a disaccharide of glucose and fructose. Sugar is used in prepared foods and it is added to some foods, in the body, sucrose is hydrolysed into the simple sugars fructose and glucose. Other disaccharides include maltose from malted grain, and lactose from milk, longer chains of sugars are called oligosaccharides or polysaccharides. Some other chemical substances, such as glycerol may also have a sweet taste, low-calorie food substitutes for sugar, described as artificial sweeteners, include aspartame and sucralose, a chlorinated derivative of sucrose. Sugars are found in the tissues of most plants and are present in sufficient concentrations for efficient commercial extraction in sugarcane, the world production of sugar in 2011 was about 168 million tonnes. The average person consumes about 24 kilograms of sugar each year, equivalent to over 260 food calories per person, since the latter part of the twentieth century, it has been questioned whether a diet high in sugars, especially refined sugars, is good for human health. Sugar has been linked to obesity, and suspected of, or fully implicated as a cause in the occurrence of diabetes, cardiovascular disease, dementia, macular degeneration, the etymology reflects the spread of the commodity. The English word sugar ultimately originates from the Sanskrit शर्करा, via Arabic سكر as granular or candied sugar, the contemporary Italian word is zucchero, whereas the Spanish and Portuguese words, azúcar and açúcar, respectively, have kept a trace of the Arabic definite article. The Old French word is zuchre and the contemporary French, sucre, the earliest Greek word attested is σάκχαρις. The English word jaggery, a brown sugar made from date palm sap or sugarcane juice, has a similar etymological origin – Portuguese jagara from the Sanskrit शर्करा. Sugar has been produced in the Indian subcontinent since ancient times and it was not plentiful or cheap in early times and honey was more often used for sweetening in most parts of the world. Originally, people chewed raw sugarcane to extract its sweetness, sugarcane was a native of tropical South Asia and Southeast Asia. Different species seem to have originated from different locations with Saccharum barberi originating in India and S. edule, one of the earliest historical references to sugarcane is in Chinese manuscripts dating back to 8th century BC that state that the use of sugarcane originated in India. Sugar was found in Europe by the 1st century AD, but only as an imported medicine and it is a kind of honey found in cane, white as gum, and it crunches between the teeth. It comes in lumps the size of a hazelnut, sugar is used only for medical purposes. Sugar remained relatively unimportant until the Indians discovered methods of turning sugarcane juice into granulated crystals that were easier to store, crystallized sugar was discovered by the time of the Imperial Guptas, around the 5th century AD

38.
Trehalose
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Trehalose, also known as mycose or tremalose, is a natural alpha-linked disaccharide formed by an α, α-1, 1-glucoside bond between two α-glucose units. Wiggers discovered trehalose in an ergot of rye, and in 1859 Marcellin Berthelot isolated it from trehala manna, a made by weevils. It can be synthesised by bacteria, fungi, plants, and it is implicated in anhydrobiosis — the ability of plants and animals to withstand prolonged periods of desiccation. It has high water retention capabilities, and is used in food, the sugar is thought to form a gel phase as cells dehydrate, which prevents disruption of internal cell organelles, by effectively splinting them in position. Rehydration then allows normal cellular activity to be resumed without the major, trehalose is not an antioxidant, because it is a non-reducing sugar and does not contain nucleophilic groups in its molecule. However, it was reported to have antioxidant effects, extracting trehalose was once a difficult and costly process, but circa the year 2000, the Hayashibara company confirmed an inexpensive extraction technology from starch for mass production. Trehalose is used in a spectrum of applications. Trehalose is a formed by a 1, 1-glucoside bond between two α-glucose units. Because trehalose is formed by the bonding of two reducing aldehyde groups, it has no capacity to participate in the Maillard reaction, there is an industrial process where trehalose is derived from corn starch. There are at least 3 biological pathways for trehalose biosynthesis, trehalose is a nonreducing sugar formed from two glucose units joined by a 1-1 alpha bond, giving it the name of α-D-glucopyranosyl--α-D-glucopyranoside. The bonding makes trehalose very resistant to hydrolysis, and therefore is stable in solution at high temperatures. The bonding also keeps nonreducing sugars in closed-ring form, such that the aldehyde or ketone end groups do not bind to the lysine or arginine residues of proteins, trehalose is less soluble than sucrose, except at high temperatures. Trehalose forms a crystal as the dihydrate, and has 90% of the calorific content of sucrose in that form. Anhydrous forms of trehalose readily regain moisture to form the dihydrate, anhydrous forms of trehalose can show interesting physical properties when heat-treated. Trehalose aqueous solutions show a concentration-dependent clustering tendency, owing to their ability to form hydrogen bonds between one another, they self-associate in water to form clusters of various sizes. Trehalose directly interacts with nucleic acids, facilitates melting of double stranded DNA,135 Trehalase deficiency is unusual in humans, except in the Greenlandic Inuit, where it occurs in 10%-15% of the population. p. 444 In nature, trehalose can be found in animals, plants, in animals, trehalose is prevalent in shrimp, and also in insects, including grasshoppers, locusts, butterflies, and bees, in which blood-sugar is trehalose. The trehalose is then broken down into glucose by the enzyme trehalase for use

Trehalose
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Trehalose

39.
Cell membranes
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The cell membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is permeable to ions and organic molecules and controls the movement of substances in. The basic function of the membrane is to protect the cell from its surroundings. It consists of the bilayer with embedded proteins. Cell membranes can be artificially reassembled, Some authors that did not believe that there was a functional permeable boundary at the surface of the cell preferred to use the term plasmalemma to the extern region of the cell. The cell membrane surrounds the cytoplasm of living cells, physically separating the components from the extracellular environment. The cell membrane also plays a role in anchoring the cytoskeleton to provide shape to the cell, fungi, bacteria, most archaea, and plants also have a cell wall, which provides a mechanical support to the cell and precludes the passage of larger molecules. The cell membrane is permeable and able to regulate what enters and exits the cell. The movement of substances across the membrane can be passive, occurring without the input of cellular energy, or active. The membrane also maintains the cell potential, the cell membrane thus works as a selective filter that allows only certain things to come inside or go outside the cell. The cell employs a number of mechanisms that involve biological membranes,1. Passive osmosis and diffusion, Some substances such as carbon dioxide and oxygen, can move across the membrane by diffusion. Because the membrane acts as a barrier for certain molecules and ions, such a concentration gradient across a semipermeable membrane sets up an osmotic flow for the water. Transmembrane protein channels and transporters, Nutrients, such as sugars or amino acids, must enter the cell, such molecules diffuse passively through protein channels such as aquaporins in facilitated diffusion or are pumped across the membrane by transmembrane transporters. Protein channel proteins, also called permeases, are quite specific, recognizing and transporting only a limited food group of chemical substances. Endocytosis, Endocytosis is the process in which cells absorb molecules by engulfing them, the plasma membrane creates a small deformation inward, called an invagination, in which the substance to be transported is captured. The deformation then pinches off from the membrane on the inside of the cell, Endocytosis is a pathway for internalizing solid particles, small molecules and ions, and macromolecules. Endocytosis requires energy and is thus a form of active transport and this is the process of exocytosis

40.
International Standard Book Number
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The International Standard Book Number is a unique numeric commercial book identifier. An ISBN is assigned to each edition and variation of a book, for example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, the method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country. The initial ISBN configuration of recognition was generated in 1967 based upon the 9-digit Standard Book Numbering created in 1966, the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108. Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure, however, this can be rectified later. Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines, the ISBN configuration of recognition was generated in 1967 in the United Kingdom by David Whitaker and in 1968 in the US by Emery Koltay. The 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108, the United Kingdom continued to use the 9-digit SBN code until 1974. The ISO on-line facility only refers back to 1978, an SBN may be converted to an ISBN by prefixing the digit 0. For example, the edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has SBN340013818 -340 indicating the publisher,01381 their serial number. This can be converted to ISBN 0-340-01381-8, the check digit does not need to be re-calculated, since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with Bookland European Article Number EAN-13s. An ISBN is assigned to each edition and variation of a book, for example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, a 13-digit ISBN can be separated into its parts, and when this is done it is customary to separate the parts with hyphens or spaces. Separating the parts of a 10-digit ISBN is also done with either hyphens or spaces, figuring out how to correctly separate a given ISBN number is complicated, because most of the parts do not use a fixed number of digits. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for country or territory regardless of the publication language. Some ISBN registration agencies are based in national libraries or within ministries of culture, in other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded. In Canada, ISBNs are issued at no cost with the purpose of encouraging Canadian culture. In the United Kingdom, United States, and some countries, where the service is provided by non-government-funded organisations. Australia, ISBNs are issued by the library services agency Thorpe-Bowker

International Standard Book Number
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A 13-digit ISBN, 978-3-16-148410-0, as represented by an EAN-13 bar code

41.
International Standard Serial Number
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An International Standard Serial Number is an eight-digit serial number used to uniquely identify a serial publication. The ISSN is especially helpful in distinguishing between serials with the same title, ISSN are used in ordering, cataloging, interlibrary loans, and other practices in connection with serial literature. The ISSN system was first drafted as an International Organization for Standardization international standard in 1971, ISO subcommittee TC 46/SC9 is responsible for maintaining the standard. When a serial with the content is published in more than one media type. For example, many serials are published both in print and electronic media, the ISSN system refers to these types as print ISSN and electronic ISSN, respectively. The format of the ISSN is an eight digit code, divided by a hyphen into two four-digit numbers, as an integer number, it can be represented by the first seven digits. The last code digit, which may be 0-9 or an X, is a check digit. Formally, the form of the ISSN code can be expressed as follows, NNNN-NNNC where N is in the set, a digit character. The ISSN of the journal Hearing Research, for example, is 0378-5955, where the final 5 is the check digit, for calculations, an upper case X in the check digit position indicates a check digit of 10. To confirm the check digit, calculate the sum of all eight digits of the ISSN multiplied by its position in the number, the modulus 11 of the sum must be 0. There is an online ISSN checker that can validate an ISSN, ISSN codes are assigned by a network of ISSN National Centres, usually located at national libraries and coordinated by the ISSN International Centre based in Paris. The International Centre is an organization created in 1974 through an agreement between UNESCO and the French government. The International Centre maintains a database of all ISSNs assigned worldwide, at the end of 2016, the ISSN Register contained records for 1,943,572 items. ISSN and ISBN codes are similar in concept, where ISBNs are assigned to individual books, an ISBN might be assigned for particular issues of a serial, in addition to the ISSN code for the serial as a whole. An ISSN, unlike the ISBN code, is an identifier associated with a serial title. For this reason a new ISSN is assigned to a serial each time it undergoes a major title change, separate ISSNs are needed for serials in different media. Thus, the print and electronic versions of a serial need separate ISSNs. Also, a CD-ROM version and a web version of a serial require different ISSNs since two different media are involved, however, the same ISSN can be used for different file formats of the same online serial

International Standard Serial Number
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ISSN encoded in an EAN-13 barcode with sequence variant 0 and issue number 5

42.
Patient UK
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Patient is an online resource providing information on health, lifestyle, disease and other medical related topics. The websites aim is to members of the public with up-to-date information on health related topics in the form of comprehensive leaflets, blogs, wellbeing advice. Leaflets are compiled by qualified medical practitioners with several years of experience in the medical profession, in 2013, the site appeared in a Top 50 websites feature published in The Times. Gordon invited the Kennys to add condition information leaflets to Mentor so these could be printed out for patients during GP consultations. In January 1998, OUP published the newly accumulated patient materials written by PiP with software developed by EMIS as the stand alone ‘Oxford PILs’ for use by non-EMIS practices, the software was designed to connected with OUP’s version of Mentor. This was done so the reputable and reliable content could be accessed by all members of the public who needed support, in April 2008, EMIS acquired PIPs share of Patient, but the companys partners remain involved as consultant editors and lead authors. EMIS continued to integrate the content with its Electronic health record systems so that patients accessing their own records can go directly to advice and information about their condition. It is accredited by The Information Standard, NHS England’s quality mark and was listed as ‘The top health website you can’t live without’ by The Times newspaper. It was launched with the intention that the service could help alert CCGs, plans are also in development for the trends box feature to be made available for GPs to host on their own surgery websites as an additional patient information service. Patient contains health-related information produced by a team of doctors, users can register with the site, allowing them to book appointments with their own GP and order repeat prescriptions. However, this is possible if the users surgery uses EMIS computer software. Information on Patient is updated to keep abreast of the latest medical evidence, the Daily Telegraph has described Patient as a gateway to some of the most reliable online health resources, while The Good Web Guide calls the site well-designed and clear. A Times article from 2007 describes the information on Patient as simple and easily accessible, in early 2012 alongside the site rebrand, Patient moved into the mobile market - producing several apps designed to allow the public to access health information on mobile devices. Patient claims to have won awards for its content over several years from different award bodies

Patient UK

43.
Temperature
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A temperature is an objective comparative measurement of hot or cold. It is measured by a thermometer, several scales and units exist for measuring temperature, the most common being Celsius, Fahrenheit, and, especially in science, Kelvin. Absolute zero is denoted as 0 K on the Kelvin scale, −273.15 °C on the Celsius scale, the kinetic theory offers a valuable but limited account of the behavior of the materials of macroscopic bodies, especially of fluids. Temperature is important in all fields of science including physics, geology, chemistry, atmospheric sciences, medicine. The Celsius scale is used for temperature measurements in most of the world. Because of the 100 degree interval, it is called a centigrade scale.15, the United States commonly uses the Fahrenheit scale, on which water freezes at 32°F and boils at 212°F at sea-level atmospheric pressure. Many scientific measurements use the Kelvin temperature scale, named in honor of the Scottish physicist who first defined it and it is a thermodynamic or absolute temperature scale. Its zero point, 0K, is defined to coincide with the coldest physically-possible temperature and its degrees are defined through thermodynamics. The temperature of zero occurs at 0K = −273. 15°C. For historical reasons, the triple point temperature of water is fixed at 273.16 units of the measurement increment, Temperature is one of the principal quantities in the study of thermodynamics. There is a variety of kinds of temperature scale and it may be convenient to classify them as empirically and theoretically based. Empirical temperature scales are historically older, while theoretically based scales arose in the middle of the nineteenth century, empirically based temperature scales rely directly on measurements of simple physical properties of materials. For example, the length of a column of mercury, confined in a capillary tube, is dependent largely on temperature. Such scales are only within convenient ranges of temperature. For example, above the point of mercury, a mercury-in-glass thermometer is impracticable. A material is of no use as a thermometer near one of its phase-change temperatures, in spite of these restrictions, most generally used practical thermometers are of the empirically based kind. Especially, it was used for calorimetry, which contributed greatly to the discovery of thermodynamics, nevertheless, empirical thermometry has serious drawbacks when judged as a basis for theoretical physics. Theoretically based temperature scales are based directly on theoretical arguments, especially those of thermodynamics, kinetic theory and they rely on theoretical properties of idealized devices and materials

44.
Effects of high altitude on humans
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The effects of high altitude on humans are considerable. The percentage oxygen saturation of hemoglobin determines the content of oxygen in blood, after the human body reaches around 2,100 m above sea level, the saturation of oxyhemoglobin begins to plummet. However, the body has both short-term and long-term adaptations to altitude that allow it to partially compensate for the lack of oxygen. Athletes use these adaptations to help their performance, there is a limit to the level of adaptation, mountaineers refer to the altitudes above 8,000 metres as the death zone, where it is generally believed that no human body can acclimatize. The human body can perform best at sea level, where the pressure is 101,325 Pa or 1013.25 millibars. The concentration of oxygen in air is 20. 9%. In healthy individuals, this saturates hemoglobin, the red pigment in red blood cells. Atmospheric pressure decreases exponentially with altitude while the O2 fraction remains constant to about 100 km, so pO2 decreases exponentially with altitude as well. It is about half of its value at 5,000 m, the altitude of the Everest Base Camp, and only a third at 8,848 m. When pO2 drops, the body responds with altitude acclimatization, the higher the altitude, the greater the risk. Research also indicates elevated risk of permanent brain damage in people climbing to extreme altitudes, expedition doctors commonly stock a supply of dexamethasone, or dex, to treat these conditions on site. Humans have survived for two years at 5,950 m, which is the highest recorded permanently tolerable altitude, at extreme altitudes, above 7,500 m, sleeping becomes very difficult, digesting food is near-impossible, and the risk of HAPE or HACE increases greatly. The death zone, in mountaineering, refers to altitudes above a point where the amount of oxygen is insufficient to sustain human life. This point is generally tagged as 8,000 m, many deaths in high-altitude mountaineering have been caused by the effects of the death zone, either directly or indirectly. In the death zone, the body cannot acclimatize. An extended stay in the zone without supplementary oxygen will result in deterioration of bodily functions, loss of consciousness, studies have shown that the approximately 140 million people who live at elevations above 2,500 metres have adapted to the lower oxygen levels. These adaptations are especially pronounced in people living in the Andes, compared with acclimatized newcomers, native Andean and Himalayan populations have better oxygenation at birth, enlarged lung volumes throughout life, and a higher capacity for exercise. Tibetans demonstrate an increase in cerebral blood flow, lower hemoglobin concentration

Effects of high altitude on humans
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Climbing Mount Rainier.
Effects of high altitude on humans
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The summit of Mount Everest is in the death zone.
Effects of high altitude on humans
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The summit of K2 is in the death zone
Effects of high altitude on humans
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Athletes training at high altitude in Switzerland

45.
Travel
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Travel can also include relatively short stays between successive movements. The origin of the travel is most likely lost to history. The term travel may originate from the Old French word travail, according to the Merriam Webster dictionary, the first known use of the word travel was in the 14th century. It also states that the word comes from Middle English travailen, travelen, in English we still occasionally use the words travail, which means struggle. According to Simon Winchester in his book The Best Travelers Tales and this link may reflect the extreme difficulty of travel in ancient times. Today, travel may or may not be much easier depending upon the destination you choose, how you plan to get there, theres a big difference between simply being a tourist and being a true world traveler, notes travel writer Michael Kasum. This is, however, a distinction as academic work on the cultures. Travel may occur by human-powered transport such as walking or bicycling, or with vehicles, such as transport, automobiles, trains. In some countries, non-local internal travel may require a passport, while international travel typically requires a passport. A trip may also be part of a round-trip, which is a type of travel whereby a person moves from one location to another. Once difficult, slow and dangerous, travel has tended to become easier, quicker, the evolution of technology such as horse tack and bullet trains has contributed to this trend. While travel in the Middle Ages offered hardships and challenges, it loomed large in the economy, pilgrimages involved streams of travellers both locally and internationally. Travel by water provided more comfort and speed than land-travel - at least until the advent of a network of railways in the 19th century. Airships and airplanes usurped much of the role of surface travel in the twentieth century. Authorities emphasize the importance of taking precautions to ensure travel safety, when traveling abroad, the odds favor a safe and incident-free trip, however, travelers can be subject to difficulties, crime and violence. Many countries do not recognize drivers licenses from other countries, however most countries accept international driving permits, automobile insurance policies issued in ones own country are often invalid in foreign countries, and it is often a requirement to obtain temporary auto insurance valid in the country being visited. It is also advisable to become oriented with the driving-rules and -regulations of destination countries, wearing a seat belt is highly advisable for safety reasons, many countries have penalties for violating seatbelt laws

46.
Dermatosis neglecta
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Dermatosis neglecta is a skin condition in which accumulation of sebum, keratin, sweat, dirt and debris leads to a localized patch of skin discoloration or a wart-like plaque. It is caused by inadequate hygiene of a body part. Dermatosis neglecta typically develops several months after a disability or other affliction leads to improper cleaning, patients may deny that negligence is the cause of the lesion, even though it completely resolves on vigorous rubbing with alcohol swabs or water and soap. Recognizing the diagnosis avoids unnecessary skin biopsies, many other conditions can lead to localized scaling or hyperpigmentation. The term was first coined by Poskitt and coworkers in 1995

Dermatosis neglecta
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A 35-year-old male of Pakistani origin, with multiple fractures, neurological deficit and immobility sustained in a fall, leading to the development of dermatosis neglecta of the left hand. Upper image: Dorsum of hand (at presentation). Lower image: Dorsum of hand (after two weeks).

47.
Electrical burn
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An electrical burn is a burn that results from electricity passing through the body causing rapid injury. Approximately 1,000 deaths per year due to injuries are reported in the United States. Electrical burns differ from thermal or chemical burns in that cause much more subdermal damage. They can exclusively cause surface damage, but more often tissues deeper underneath the skin have been severely damaged, as a result, electrical burns are difficult to accurately diagnose, and many people underestimate the severity of their burn. In extreme cases, electricity can cause shock to the brain, strain to the heart, for a burn to be classified as electrical, electricity must be the direct cause. For example, burning a finger on a hot electric steam iron would be thermal, electricity passing through resistance creates heat, so there is no current entering the body in this type of burn. Likewise, a fire that is ruled to be electrical in origin, unless someone was injured at the exact moment that the fire began, it is unlikely that any electrical burns would occur. Also, swallowed button cell battery injuries are sometimes confused as electrical burns, the small voltage in the batteries is not nearly enough to produce a burn. However, through a known as electrolysis, salt water exposed to an electric current produces sodium hydroxide. This in turn, causes a serious, sometimes fatal chemical burn, four electrical factors determine the severity of the damage caused by electrical burns, voltage, current, resistance, and frequency. The severity of the burn also depends on the pathway the current takes through the body, generally, the pathway of the current will follow the course the least resistant tissues, firstly blood vessels, nerves, and muscle, then skin, tendon, fat, and bone. Most commonly, electric injuries primarily damage the outer limbs, as the body comes into contact with an electrical source, it becomes part of the electrical circuit. As such, the current has a point of entry and an exit at two different points on the body, the point of entry tends to be depressed and leathery whereas the exit wound is typically more extensive and explosive. It is hard to diagnose an electrical burn because only the entry and exit wounds are visible. Lightning strikes are also a cause of burns, but this is a less common event. With the advances in technology, electrical injuries are becoming common and are the fourth leading cause of work-related traumatic death. One third of all electrical traumas and most high-voltage injuries are job related, electrical burns can be classified into six categories, and any combination of these categories may be present on an electrical burn victim, Low-voltage burn. A burn produced by contact with a source of 500 volts or less is classified as a low-voltage burn

Electrical burn
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Electrical burn on hand

48.
Freediving
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There are also a range of competitive apnea disciplines, in which competitors attempt to attain great depths, times, or distances on a single breath. In ancient times freediving without the aid of devices was the only possibility, with the exception of the occasional use of reeds. The divers faced the problems as divers today, such as decompression sickness. Freediving was practised in ancient cultures to gather food, harvest resources like sponge and pearl, reclaim sunken valuables, in Ancient Greece, both Plato and Homer mention the sponge as being used for bathing. The island of Kalymnos was a centre of diving for sponges. By using weights of as much as 15 kilograms to speed the descent, harvesting of red coral was also done by divers. The Mediterranean had large amounts of maritime trade, as a result of shipwrecks, particularly in the fierce winter storms, divers were often hired to salvage whatever they could from the seabed. Divers would swim down to the wreck and choose the most valuable pieces to salvage, divers were also used in warfare. Defenses against sea vessels were often created, such as underwater barricades -, if barricades were found, it was divers who were used to disassemble them, if possible. In Japan, the Ama divers began to collect pearls about 2,000 years ago. For thousands of years, most seawater pearls were retrieved by divers working in the Indian Ocean, in such as the Persian Gulf, the Red Sea. A fragment of Isidore of Charaxs Parthian itinerary was preserved in Athenaeuss 3rd-century Sophists at Dinner, Pearl divers near the Philippines were also successful at harvesting large pearls, especially in the Sulu Archipelago. At times, the largest pearls belonged by law to the sultan, nonetheless many pearls made it out of the archipelago by stealth, ending up in the possession of the wealthiest families in Europe. Pearling was popular in Qatar, Bahrain, Japan, and India, the Gulf of Mexico was also known for pearling. Spearfishing is an ancient method of fishing that has used throughout the world for millennia. Early civilizations were familiar with the custom of spearing fish from rivers, today modern spearfishing makes use of elastic powered spearguns and slings, or compressed gas pneumatic powered spearguns, to strike the hunted fish. Specialised techniques and equipment have been developed for various types of aquatic environments, spearfishing may be done using free-diving, snorkelling, or scuba diving techniques. Spearfishing while using scuba equipment is illegal in some countries, the use of mechanically powered spearguns is also outlawed in some countries and jurisdictions

Freediving
–
Freediver with monofin, ascending
Freediving
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Natural sponges have been harvested by freedivers near the Greek island of Kalymnos since at least the time of Plato.
Freediving
–
Monofin freediver holding his breath and swimming underwater
Freediving
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Herbert Nitsch, World Record Holder Freediver

49.
Scuba diving
–
Scuba diving is a mode of underwater diving in which the scuba diver uses a self-contained underwater breathing apparatus which is completely independent of surface supply, to breathe underwater. They may include additional cylinders for decompression gas or emergency breathing gas, closed-circuit or semi-closed circuit rebreather scuba systems allow recycling of exhaled gases. The volume of gas used is reduced compared to that of open circuit, therefore, scuba divers engaged in armed forces covert operations may be referred to as frogmen, combat divers or attack swimmers. A scuba diver primarily moves underwater by using fins attached to the feet, scuba divers are trained in the procedures and skills appropriate to their level of certification by instructors affiliated to the diver certification organisations which issue these certifications. A minimum level of fitness and health is required by most training organisations, the closed-circuit rebreathers were first developed for escape and rescue purposes, and were modified for military use, due to their stealth advantages, as they produce very few bubbles. The first commercially successful closed-circuit scuba was designed and built by English diving engineer, Henry Fleuss in 1878, while working for Siebe Gorman in London. Sir Robert Davis, head of Siebe Gorman, improved the oxygen rebreather in 1910 with his invention of the Davis Submerged Escape Apparatus, rebreathers have been increasingly used by civilians for recreation, especially since the end of the Cold War. This reduced the risk of attack by Communist Bloc forces. After that, the armed forces had less reason to requisition civilian rebreather patents. The single hose two stage scuba regulators trace their origins to Australia, where Ted Eldred developed the first example of type of regulator. This was developed because patents protected the Aqualungs twin hose design, the single hose regulator separates the demand valve from the cylinder, giving the diver air at the ambient pressure at the mouth, rather than ambient pressure at the cylinder valve. The term SCUBA originally referred to United States combat frogmens oxygen rebreathers, SCUBA was originally an acronym, but is now generally used as a common noun or adjective, scuba. It has become acceptable to refer to equipment or scuba apparatus—examples of the linguistic RAS syndrome. Scuba diving may be performed for a number of reasons, both personal and professional, recreational diving is done purely for enjoyment and has a number of technical disciplines to increase interest underwater, such as cave diving, wreck diving, ice diving and deep diving. Divers may be employed professionally to perform tasks underwater, some of these tasks are suitable for scuba. There are divers who work, full or part-time, in the diving community as instructors, assistant instructors, divemasters. Other specialist areas of diving include military diving, with a long history of military frogmen in various roles. Their roles include direct combat, infiltration behind enemy lines, placing mines or using a manned torpedo, in some cases diver rescue teams may also be part of a fire department, paramedical service or lifeguard unit, and may be classed as public service diving

50.
Altitude diving
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Altitude diving is underwater diving using scuba or surface supplied diving equipment where the surface is 300 meters or more above sea level. Altitude is significant in diving because the depths and decompression used for dives at altitude are different from those used for the dive profile at sea level. Special consideration must be given to measurement of depth given the effect of pressure on gauges, the use of bourdon tube, diaphragm, and digital depth gauges may require adjustment for use at altitude. Capillary gauges have been shown to be a method for measurement of compensated depth at altitude. Modern dive computers detect changes in altitude and automatically adjust their calculation of a safe decompression regime for a dive at that altitude, if an altitude-aware computer is not used, altitude decompression tables must be used. The dives are typically carried out in freshwater at altitude so it has a lower density than seawater used for calculation of decompression tables. The amount of time the diver has spent acclimatising at altitude is also of concern as divers with gas loadings near those of sea level may also be at an increased risk, the US Navy recommends waiting 12 hours following arrival at altitude before performing the first dive. The Cross Corrections were later looked at by Bassett and by Bell, hennessy formulated that it was possible to convert standard air decompression tables for no-stop diving at altitude or from a habitat based on phase equilibration theory. Albert A. Bühlmann recognized the problem and proposed a method which calculated maximum nitrogen loading in the tissues at an ambient pressure. Wienke proposed guidelines for decompression diving at altitude in 1993, egi and Brubakk reviewed various models for preparing tables for diving at altitude. Paulev and Zubieta have created a new factor in order to make any sea level dive table usable during high altitude diving in 2007. Repetitive dives should be conducted in the manner as other dives including Cross Corrections for altitude. The US Navy does not allow repetitive diving for surface-supplied helium-oxygen diving, an 18-hour surface interval is required if the dive requires decompression. In addition to making depth adjustments using the Cross Conversions, dives at altitude often require pre-, several methods for performing post-dive ascents are used. One is to adjust the times needed for an altitude ascent. Another is to use surface intervals to allow for an ascent and this record was equalled by a team led by Nathalie Cabrol in 2006. That year, Cabrol set the highest recorded altitude scuba diving for women and she also free dived at Lake Licancabur in 2003 and 2004. In 2007, a new record was set in the lagoon located near the summit of Pili Volcano, at just over 6,000 metres, by Philippe Reuter, Claudia Henríquez

51.
Cave diving
–
Cave diving is underwater diving in water-filled caves. It may be done as a sport, a way of exploring flooded caves for scientific investigation, or for the search for. Recreational cave diving is considered to be a type of technical diving due to the lack of a free surface during large parts of the dive. It originated in the United Kingdom, stemming from the more common activity of caving and its origins in the United States are more closely associated to scuba diving. Compared to caving and scuba diving, there are relatively few practitioners of cave diving and this is due in part to the specialized equipment and skill sets required, and in part because of the high potential risks due to the specific environment. Despite these risks, water-filled caves attract scuba divers, cavers, and speleologists due to their often unexplored nature, Underwater caves have a wide range of physical features, and can contain fauna not found elsewhere. The procedures of cave diving have much in common with procedures used for types of penetration diving. This is ensured by the use of a continuous guideline between the team and outside of the flooded cave, and diligent planning and monitoring of gas supplies. Two basic types of guideline are used, permanent lines, permanent lines may include a main line starting near the entrance/exit, and side lines or branch lines, and are marked to indicate the direction to the nearest exit. Temporary lines include exploration lines and jump lines, in some caves, changes of depth of the cave along the dive route will constrain decompression depths, and gas mixtures and decompression schedules can be tailored to take this into account. Most open-water diving skills apply to diving, and there are additional skills specific to the environment. Good buoyancy control, trim and finning technique help preserve visibility in areas with silt deposits, the ability to navigate in total darkness using the guideline to find the way out is a safety critical emergency skill. Emergency skills for dealing with gas supply problems are complicated by the possibility of the emergency occurring in a confined space, Cave diver training also stresses the importance of risk management and cave conservation ethics. Most training systems offer progressive stages of education and certification, Cavern training covers the basic skills needed to enter the overhead environment. Training will generally consist of gas planning, propulsion techniques needed to deal with the silty environments in many caves, reel and handling, and communication. Once certified as a diver, a diver may undertake cavern diving with a cavern or cave certified buddy. Once intro to cave certified, a diver may penetrate further into a cave, usually limited by 1/3 of a single cylinder, or in the case of a basic cave certification. An intro cave diver is not certified to do complex navigation

52.
Deep diving
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Deep diving has different meanings depending on the context. For some recreational diving agencies, Deep diving, or Deep diver may be a certification awarded to divers that have trained to dive to a specified depth range. In technical diving, a depth below about 60 metres where hypoxic breathing gas becomes necessary to avoid oxygen toxicity may be considered a deep dive, in professional diving, a depth that requires special equipment, procedures, or advanced training may be considered a deep dive. Deep diving can mean something else in the commercial diving field, for instance early experiments carried out by Comex S. A. using hydrox and trimix attained far greater depths than any recreational technical diving. One example being the Comex Janus IV open-sea dive to 501 metres in 1977 and these divers needed to breathe special gas mixtures because they were exposed to very high ambient pressure. An atmospheric diving suit allows very deep dives of up to 2,000 feet and these suits are capable of withstanding the pressure at great depth permitting the diver to remain at normal atmospheric pressure. This eliminates the problems associated with breathing high-pressure gases, Deep diving has more hazards and greater risk than basic open water diving. Nitrogen narcosis, the “narks” or “rapture of the deep”, starts with feelings of euphoria and over-confidence but then leads to numbness and memory impairment similar to alcohol intoxication. Decompression sickness, or the “bends”, can happen if a diver ascends too fast and these bubbles produce mechanical and biochemical effects that lead to the condition. The onset of symptoms depends on the severity of the gas loading and may develop during ascent in severe cases. Bone degeneration is caused by the bubbles forming inside the bones, most commonly the upper arm, Deep diving involves a much greater danger of all of these, and presents the additional risk of oxygen toxicity, which may lead to a convulsion underwater. Very deep diving using a helium–oxygen mixture carries a risk of high-pressure nervous syndrome, coping with the physical and physiological stresses of deep diving requires good physical conditioning. Using normal scuba equipment, breathing gas consumption is proportional to ambient pressure - so at 50 metres, where the pressure is 6 bar, the need to do decompression stops increases with depth. A diver at 6 metres may be able to dive for many hours without needing to do decompression stops, at depths greater than 40 metres, a diver may have only a few minutes at the deepest part of the dive before decompression stops are needed. In the event of an emergency the diver cannot make an ascent to the surface without risking decompression sickness. All of these result in the amount of breathing gas required for deep diving being much greater than for shallow open water diving. The diver needs a disciplined approach to planning and conducting dives to minimise these additional risks, both equipment and procedures can be adapted to deal with the problems of greater depth. Usually the two are combined, as the procedures must be adapted to suit the equipment, and in cases the equipment is needed to facilitate the procedures

53.
Ice diving
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Ice diving is a type of penetration diving where the dive takes place under ice. Because diving under ice places the diver in an overhead environment typically with only a single point, it requires special procedures. Ice diving is done for purposes of recreation, scientific research, public safety, the most obvious hazards of ice diving are getting lost under the ice, hypothermia, and regulator failure due to freezing. Scuba divers are generally tethered for safety and this means that the diver wears a harness to which a line is secured, and the other end of the line is secured above the surface and monitored by an attendant. For the surface team, the hazards include freezing temperatures. Whether ice diving inherently constitutes technical diving is debated within the diving community. For the professional diver it is a high risk environment requiring additional safety measures, Ice diving is a team diving activity because each divers lifeline requires a line tender. This person is responsible for paying out and taking in line so that the diver does not get tangled, in these cases the divers should be competent in procedures for diving with a guideline. Polar diving experience has shown that control is a critical skill affecting safety. Typical procedure for a dive under ice, A snow shovel is used to clear the snow. An ice saw or a chain saw is used to cut a hole in the ice, a weatherproof area is used for the divers to suit up. The diver and tender on the surface are connected by a rope lifeline, the harness fits over the shoulders and around the back such that the tender on the surface can, in an emergency, haul an unconscious diver back to the hole. The harness should not be able to slide up or down the torso when pulled in line with the body. Rope signals or voice communications systems must be used, a roped standby diver is ready on the surface. One or two divers may dive at the time from the same hole, each with his or her own rope. Using two ropes runs little risk of getting tangled together, but using three significantly increases this risk, If the regulator free-flows and freezes, the diver should close it down and switch to the backup, and terminate the dive. When diving in pack ice, the team must constantly monitor ice movement to ensure that the exit is not compromised. The diver must ensure there is always a positive indication of the route to the exit area

54.
Gas blending
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Gas blending is the process of mixing gases for a specific purpose where the composition of the resulting mixture is specified and controlled. A wide range of applications include scientific and industrial processes, food production and storage, Gas mixtures are usually specified in terms of molar gas fraction, by percentage, parts per thousand or parts per million. Volumetric gas fraction converts trivially to partial pressure ratio, following Daltons law of partial pressures, both partial pressure and mass fraction blending are used in practice. Gas tungsten arc welding, or tungsten inert gas welding, is a welding process that uses a nonconsumable tungsten electrode, an inert or semi-inert gas mixture. The gas composition used to food products depends on the product. A high oxygen content helps to retain the red colour of meat, while low oxygen reduces mould growth in bread, sparging, An inert gas such as nitrogen is bubbled through the wine, which removes the dissolved oxygen. Carbon dioxide is removed and to ensure that an appropriate amount of carbon dioxide remains. A breathing gas is a mixture of chemical elements and compounds used for respiration. The essential component for any breathing gas is a pressure of oxygen of between roughly 0.16 and 1.60 bar at the ambient pressure. The oxygen is usually the only metabolically active component unless the gas is an anaesthetic mixture, Gas blending for scuba diving is the filling of diving cylinders with non-air breathing gases such as nitrox, trimix and heliox. Use of these gases is generally intended to improve safety of the planned dive, by reducing the risk of decompression sickness and/or nitrogen narcosis. Part of the operation of the system is the replenishment of oxygen used by the occupants. This entails monitoring of the composition of the gas and periodic addition of oxygen to the chamber gas at the internal pressure of the chamber. The gas mixing and delivery system lets the anesthetist control oxygen fraction, nitrous oxide concentration, air is used as a diluent to decrease oxygen concentration. In special cases other gases may also be added to the mixture and these may include carbon dioxide, used to stimulate respiration, and helium to reduce resistance to flow or to enhance heat transfer. Gas mixing systems may be mechanical, using conventional rotameter banks, or electronic, using proportional solenoids or pulsed injectors, examples include melting of reactive metals such as magnesium, and heat treatment of steels. Calibration gases, Span gases are used for testing and calibrating gas detection equipment by exposing the sensor to a concentration of a contaminant. Zero gas is normally a gas free of the component to be measured, calibration gas mixtures are generally produced in batches by gravimetric or volumetric methods

55.
Muck diving
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Muck diving gets its name from the sediment that lies at the bottom of many dive sites - a frequently muddy or mucky environment. Other than muddy sediment, the muck dive substrate may consist of dead coral skeletons, discarded fishing equipment, tires, in addition, the visibility is usually less to the reef or wreck sites of the area. The term muck diving was first used by Bob Halstead to describe diving off the beaches made up of sand in Milne Bay. The muck substrate can be the habitat for unusual, exotic and juvenile organisms that make their homes in the sediment, the sediment and detritus environment has a different ecology to the reef. Creatures like colorful nudibranchs, anglerfish, shrimp, blue-ringed octopus, the most popular region for muck diving is Southeast Asia, where there are more marine species than anywhere else in the world. Other sedimentary bottom habitats may also provide interesting ecologies, and muck diving is possible almost anywhere that recreational diving is possible, perhaps those that enjoy muck diving the most are the macro photographers. The calm and shallow water provides amazing opportunities to photograph the creatures that hide amongst the muck

Muck diving
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Modes

56.
Open-water diving
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In underwater diving, open water is unrestricted water such as a sea, lake or flooded quarries. It is the opposite of confined water where diver training takes place, open water also means the diver has direct vertical access to the surface of the water in contact with the Earths atmosphere. Open water diving implies that if a problem arises, the diver can directly ascend vertically to the atmosphere to breathe air, penetration diving—involving entering caves or wrecks, or diving under ice—is therefore not open water diving. and the range of hazards and associated risk is significantly expanded. In this context confined water is a case of open water. Some recreational diver certification agencies use a variation on this term in the title of their entry level certification

Open-water diving
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Modes

57.
Sidemount diving
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Sidemount is a scuba diving equipment configuration which has scuba sets mounted alongside the diver, below the shoulders and along the hips, instead of on the back of the diver. These benefits for operating in confined spaces were also recognized by divers who conducted technical wreck diving penetrations. Sidemount diving Sidemount diving is the practice of diving with two or more cylinders secured at the sides of the body in line with the torso and without cylinders on the diver’s back. A common characteristic of the sidemount configuration is the use of bungee cords hooked over the valve to keep it tucked in close to the armpit. These bungees are normally routed from behind the upper back to a chest D-ring. The lower part of the cylinder is secured to the diver’s harness near the waist or hips by bolt snaps clipped to a butt-plate or waistband D-rings, Monkey diving Monkey diving is the use of sidemount configuration and procedures with a single cylinder. It is presented as an option on some recreational level sidemount courses, the use of a single cylinder may require counter-weighting to prevent lateral instability in the water, depending on the buoyancy of the chosen cylinder, and does not provide a redundant gas supply. No-mount diving No-mount diving is a specialized overhead-environment strategy for dealing with particularly tight restrictions and this may involve divers wearing a very basic harness under their existing configuration, or simply hand-carrying cylinders. A ‘no-mount’ harness can consist of nothing more than a weight-belt with several D-rings attached, the evolution of sidemount techniques and configurations has largely made this approach unnecessary, as a minimalist sidemount harness/BCD can be worn beneath back-mounted doubles, or even a CCR. Sidemount diving offers some benefits in the flexibility of equipment, when diving in remote locations, the transportation of single diving cylinders, especially by hand, may be less physically taxing. Sidemount harness can be lighter and less bulky than back-mounted alternatives – allowing for easier and cheaper air travel, unlike back-mounted cylinders, the sidemount diver has immediate access to, and can see, the regulators and tank valves of their cylinders. Streamlining for reduced drag while swimming is not always achieved, mounting the cylinders at the diver’s sides reduces exposure of valves and regulator first-stages to impact and abrasion damage, or accidental shut-down through roll-off against a ceiling. It also significantly reduces the risk of entanglement behind the diver, some divers will testify that sidemount diving configuration offers greater stability and easier-to-attain trim and control in the water. It is also claimed to be physically tiring to carry. The ability to attach, remove and replace cylinders while in the water allows the diver to avoid carrying twinned cylinders, the reduced physical exertion when conducting regulator shut-down procedures is a major benefit to divers who suffer from shoulder or back discomfort or reduced mobility. Technical divers have used a redundant gas supply system, either isolation-manifolded or independent back-mounted cylinders. Recreational divers have traditionally resorted to using buddy supplied gas, or relatively small bailout ‘pony cylinders’ or ‘ascent bottles’ for out-of-air emergencies. Sidemount diving with two equal-sized cylinders helps resolve stability and streamlining issues, and can ensure that an adequate redundant reserve of air is maintained, back-mounted manifolded cylinders provide easy access to the whole gas supply in the event of a regulator failure and shut-down

58.
Wreck diving
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Wreck diving is recreational diving where the wreckage of ships, aircraft and other artificial structures are explored. Although most wreck dive sites are at shipwrecks, there is a trend to scuttle retired ships to create artificial reef sites. Diving to crashed aircraft can also be considered wreck diving, the recreation of wreck diving makes no distinction as to how the vessel ended up on the bottom. Some wreck diving involves penetration of the wreckage, making an ascent to the surface impossible for a part of the dive. These categorisations broadly coincide with the division between recreational wreck diving and technical wreck diving. Wrecks may present a variety of hazards to divers. Wrecks are often fouled by fishing lines or nets and the structure may be fragile, penetration diving, where the diver enters a shipwreck is an activity exposing the diver to hazards of getting lost, entrapment and consequently running out of breathing gas. Management of these risks requires special skills and equipment, many attractive or well preserved wrecks are in deeper water requiring deep diving precautions. If penetrating a wreck, a guideline tied off before entering a wreck, a guideline can help a diver to find the way out more easily in case of low visibility. Most wreck divers use a minimum of the rule-of-thirds for gas management and this allows for 1/3 of the gas down and into the wreck, 1/3 for exit and ascent and 1/3 reserve. Good buoyancy control is necessary for safe and non-destructive diving in the environment of a wreck, there are several methods for getting the divers to the wreck. The preferred method will depend on local conditions, when it is important to get back to the shotline for ascent, it may be tied in to the wreckage by the first divers on site using a guide-line, which is retrieved by the last divers to leave. When there is a current, it may be necessary to drop in from up-current. The wreck may be first marked with a shotline, if this is considered useful or necessary, divers may surface on the shotline, anchorline or personal DSMB depending on the conditions. When using the line to control ascents and descents, a tag line may be used between the anchor line and the stern of the vessel, to allow secure transfer between these points in a current. When live-boating there are methods for descent, including free drop. In technical penetration diving, there are two approaches. The conventional approach involves the use of continuous guidelines laid from a reel, tied just outside the entrance point, just inside the entrance point

59.
Dive computer
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Several algorithms have been used, and various personal conservatism factors may be available. Some dive computers allow for gas switching during the dive, audible alarms may be available to warn the diver when exceeding the no-stop limit, the maximum operating depth for the gas mixture, or the recommended ascent rate. The display provides data to allow the diver to avoid decompression, to decompress relatively safely, Dive computers may be wrist-mounted or fitted to a console with the submersible pressure gauge. This recorded information can be used for the divers personal log of their activities or as important information in medical review or legal cases following diving accidents. Because of the ability to continually re-calculate based on changing data. So-called multi-level dives can be planned with traditional dive tables, but the calculations become complex. Computers allow for a amount of spontaneity during the dive. Dive computers are used to calculate decompression schedules in recreational, scientific. There is no reason to assume that they cannot be valuable tools for commercial diving operations, Dive computers are battery-powered computers within a watertight and pressure resistant case. These computers track the dive profile by measuring time and pressure, all dive computers measure the ambient pressure to model the concentration of gases in the tissues of the diver. The computer uses the pressure and time input in an algorithm to estimate the partial pressure of inert gases that have been dissolved in the divers tissues. The decompression algorithms used in dive computers vary between manufacturers and computer models, the algorithm may be a variation of one of the standard algorithms, for example, several versions of the Bühlmann decompression algorithm are in use. The algorithm used may be an important consideration in the choice of a dive computer, Dive computers using the same internal electronics may be marketed under a variety of brand names. The algorithm used is intended to keep the risk of sickness to an acceptable level. Researchers use experimental diving programmes or data that has recorded from previous dives to validate an algorithm. The dive computer measures depth and time, then uses the algorithm to determine decompression requirements, an algorithm takes into account the magnitude of pressure reduction, repetitive exposures, rate of ascent, and time at altitude. As of 2012, Cochran EMC-20H, 20-tissue Haldanean model, Cochran VVAL-18, nine-tissue Haldanean model with exponential ongasing and linear offgasing. Delta P, 16-tissue Haldanean model with VGM, Mares, 10-tissue Haldanean model with RGBM, the RGBM part of the model adjusts gradient limits in multiple-dive scenarios through reduction factors

60.
Dive light
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A dive light is a light source carried by an underwater diver to illuminate the underwater environment. Scuba divers generally carry self-contained lights, but surface supplied divers may carry lights powered by cable supply, by using artificial light, it is possible to view an object in full color at greater depths. Water is responsible for the attenuation of light due to absorption so use of a light will improve a divers underwater vision. As the depth increases, more light is absorbed by the water, color absorption depends on the purity of the water - pure water is most transparent to blue frequencies, but impurities may reduce this significantly. Color vision is affected by turbidity and larger particulate matter. Early underwater lights were fixed electric flood lamps or portable lamps with dry batteries for use by divers in standard diving dress. Siebe Gorman & Company Ltd developed a model of portable lamp with a lens and attached to the divers corselet via a ball. In 1906, the filament was introduced and used to produce 200 to 3,000 candlepower dive lights. The Siebe Gorman & Company introduced a 250-watt mercury vapor lamp in 1919 that could produce as much as 18,000 candles. For diving in water, 45-watt Sodium hand lamps became the preferred choice. These early lights had to be turned on underwater to avoid cracking the glass as it entered cold water. The first lantern available to the US Navy had 150 candlepower, the early testing showed a need to increase the length of cable on the US Navy Standard Lantern from 125 feet to 250 feet in 1915 to allow for greater operational range. The United States Navy Experimental Diving Unit continues to dive lights for wet and dry illumination output, battery duration, watertight integrity. A modern dive light usually has an output of at least about 100 lumens, bright dive lights have values from about 2500 lumens. Halogen lamps provide this light at over 50W power consumption, high-intensity discharge lamps and Light-emitting diodes can provide similar output for less power. The light source and the power supply are housed in the same water, head mount lights are used by divers who need to use both hands for other purposes. This can be work by a commercial diver, or getting through tight restrictions for a cave or wreck diver. Helmet mounts are common for work which is often monitored by a helmet mount closed circuit video camera

61.
Diver propulsion vehicle
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A diver propulsion vehicle is an item of diving equipment used by scuba and rebreather divers to increase range underwater. A DPV usually consists of a pressure-resistant watertight casing containing an electric motor. There are also DPV accessories that can be mounted to a DPV accessory board to make your DPV more useful, Dive gear such as compasses, cameras, lobster sticks and even spearguns can also be mounted to DPVs. Military applications include delivery of combat divers and their equipment over distances or at speeds that would be otherwise impracticable, DPV operation requires more situational awareness than simply swimming and operating a DPV requires simultaneous depth control, buoyancy adjustment, monitoring of breathing gas, and navigation. If the diver does not control the DPV properly, an ascent or descent under power can result in barotrauma. Many forms of marine life are very well camouflaged or hide well and are only seen by divers who move very slowly. The most common type of DPV tows the diver who holds onto handles on the stern or bow, tow-behind scooters are most efficient by placing the diver parallel to and above the propeller wash. The diver wears a harness that includes a crotch-strap with a D-ring on the front of the strap, the scooter is rigged with a tow leash that clips to the scooter with releasable metal snap. These are torpedo or fish-shaped vehicles for one or more divers typically sitting astride them or in hollows inside, the well known human torpedo or chariot was used by commando frogmen in World War II. Similar vehicles have made for work divers or sport divers but better streamlined as these do not have warheads. Some Farallon and Aquazepp scooters are torpedo-shaped with handles near the bow, the Russian Protei-5 and Proton carry the diver attached to the top. The New Zealand made Proteus is strapped onto the divers cylinder, the Subskimmer is a submersible rigid-hulled inflatable boat. On the surface it is powered by an engine, when submerged the petrol engine is sealed. It can self inflate and deflate, transforming itself from a fast, light, started in the 1970s by Submarine Products Ltd. of Hexham, Northumberland, England, Subskimmer is now a tradename owned by Marine Specialised Technology. As DPVs get bigger they gradually merge into submarines, a wet sub is a small submarine where the pilots seat is flooded and the diver must wear diving gear. Covert military operations use swimmer delivery vehicles to deliver and retrieve operators into harbors, an example is the Multi-Role Combatant Craft. These are unpowered boards towed by a boat with two ropes. The diver holds onto it and keeps it submerged by adjusting the angle like an upside-down aerofoil and it is named after the manta ray fish

62.
Diving air compressor
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A low pressure diving air compressor usually has a delivery pressure of up to 30 bar, which is regulated to suit the depth of the dive. A high pressure diving compressor has a pressure which is usually over 150 bar. The pressure is limited by a valve which may be adjustable. High pressure diving compressors are generally three- or four-stage-reciprocating air compressors that are lubricated with a mineral or synthetic compressor oil free of toxic additives. Oil-lubricated compressors must only use lubricants specified by the manufacturer as suitable for use with breathing air. Special filters are used to clean the air of most residual oil, most oil lubricated compressors will have a wet sump at the bottom of the crankcase, and require the oil level to be within limits indicated by a sight glass or dipstick for proper lubrication. The compressor should also be level within the manufacturers specification while operating and these constraints ensure that the lubricant is in the right place for either the moving parts to contact it for splash lubrication, or for reliable suction to the oil pump. Low pressure diving compressors are usually single stage compressors as the pressure is relatively low. The compressed air output by the compressor must be filtered to make it fit for use as a breathing gas, for this reason, compressors must be carefully designed and maintained to ensure that oil contamination of the breathing gas is within safe limits. Oils used should be approved by the manufacturer and rated as safe for breathing air compressors. A range of mineral based and synthetic oils are supplied by several lubricant manufacturers for this application, carbon monoxide is a gas that is present in the exhaust gas of internal combustion engines, including those often used to drive compressors. It also comes from the breakdown of lubricating oil when compressors run too hot, CO is odorless, colorless, and tasteless. CO is deadly even in small quantities, because it binds with the hemoglobin in red blood cells. Breathing air compressors must be designed and placed so that the compressors intake is located in fresh air well away. Periodically, the air produced by a compressor must be tested to ensure it meets air purity standards, frequency of testing, contaminants that must be analysed, and the allowable limits vary between applications and jurisdictions. Surface supplied diving compressors are low-pressure and high-volume and they supply breathing air directly to a diver, through a control panel sometimes called a rack via a hose which is usually part of a group of hoses and cables called an umbilical. Their output is generally between 6 and 20 bar /100 and 300 psi and these compressors must be sufficiently powerful to deliver gas at a sufficient pressure and volume for multiple divers working at depths of up to about 60 m. Compressors used to fill scuba cylinders have a delivery pressure

Diving air compressor
–
A small stationary high pressure diving air compressor installation
Diving air compressor
–
A small scuba filling and blending station supplied by a compressor and storage bank
Diving air compressor
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A low pressure breathing air compressor used for surface supplied diving at the surface control point
Diving air compressor
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Filling a cylinder from the panel

63.
Diving helmet
–
Diving helmets are worn mainly by professional divers engaged in surface supplied diving, though many models can be adapted for use with scuba equipment. If a helmeted diver becomes unconscious but is breathing, the helmet will remain in place. In contrast, the scuba regulator typically used by recreational divers must be held in the mouth, otherwise it can fall out of a divers mouth. Before the invention of the regulator, all diving helmets used a free-flow design. Gas was delivered at a constant rate, regardless of the divers breathing, most modern helmets incorporate a demand valve so the helmet only delivers breathing gas when the diver inhales. Free-flow helmets use much larger quantities of gas than demand helmets and they also produce a constant noise inside the helmet, which can cause communication difficulties. Most modern helmet designs are sealed at the using a neoprene neck dam which is independent of the suit. When a neck dam is installed into a drysuit, however, when divers must work in hazardous environments such as sewage or dangerous chemicals, a helmet is sealed to a special drysuit to completely isolate and protect the diver. This equipment is the equivalent of the historic Mark V Standard Diving Dress. The first successful diving helmets were produced by the brothers Charles, inspired by a fire accident he witnessed in a stable in England, he designed and patented a Smoke Helmet to be used by firemen in smoke-filled areas in 1823. The apparatus comprised a helmet with an attached flexible collar. A long leather hose attached to the rear of the helmet was to be used to supply air - the original concept being that it would be pumped using a double bellows, a short pipe allowed breathed air to escape. The garment was made of leather or airtight cloth, secured by straps, the brothers lacked money to build the equipment themselves, so they sold the patent to their employer, Edward Barnard. In 1827, the first smoke helmets were built, by German-born British engineer Augustus Siebe, in 1828 the brothers decided to find another application for their device and converted it into a diving helmet. They marketed the helmet with an attached diving suit so that a diver could perform salvage work. In 1829 the Deane brothers sailed from Whitstable for trials of their new underwater apparatus, in 1834 Charles used his diving helmet and suit in a successful attempt on the wreck of Royal George at Spithead, during which he recovered 28 of the ships cannon. In 1836, John Deane recovered from the discovered Mary Rose shipwreck timbers, guns, longbows, in the 1830s the Deane brothers asked Siebe to apply his skill to improve their underwater helmet design. Expanding on improvements made by another engineer, George Edwards, Siebe produced his own design

64.
Diving shot
–
A diving shot, or more formally, diving shot line is an item of diving equipment consisting of a weight, a line and a buoy. The weight is dropped on the dive site and it may be tethered to the main shot line at a convenient depth. It is used for decompression and frees the main line for other divers. The lazy shots line does not need to be longer than the depth and is often only deep enough for the longer stops. It only needs a heavy enough to provide diver buoyancy control. Divers can use the line to help buoyancy control, to ease long decompression stops, the buoy marks the dive site for the people on the surface, who are generally on the dive boat, who provide safety cover for the divers. This helps them focus on the place where the divers are likely to return to the surface, several configurations are in general use, depending on the conditions. The basic shotline has a line fixed to the weight and the float and this is adequate in many circumstances, and has the advantage of simplicity. If there is any current or wind, the buoy will drift until tension in the line prevents further movement, large waves will cause the buoy and the top end of the line to bob up and down, jerking on the line. A bottom tensioned shotline controls the tension of the line in one of two ways, A length of heavy chain may be used between the bottom of the line and the shot. This chain should be enough to take up any depth variations due to tides or waves. The weight of the chain pulls down on the shotline whenever part of the chain is off the bottom, maintaining some tension, the length of line must be adjusted so that some chain is always suspended, but never all. The other method is to run the line through a loop on the weight, the float must either be sufficiently rigid to withstand the pressure, or an open bag inflated at the bottom by a diver. When this method is used a shot is generally necessary. Top tensioning is achieved by running the line through a loop on the buoy and this weight will hang down and double its weight will pull on the float due to the mechanical advantage of the system. This is not usually a problem, as it is relatively easy to get a buoy of adequate volume. A lazy shot is a shotline that does not reach the bottom, the weight hangs suspended from the surface and the line is used to provide a decompression station. A lazy shot may be hung from a buoy, a boat or a structure as circumstances warrant, the lazy shot may be tethered to the main shotline and unclipped to drift after the last diver has reached it

65.
Diving weighting system
–
Divers wear weighting systems, weight belts or weights to counteract the buoyancy of other diving equipment, such as diving suits and aluminium diving cylinders. During the dive, buoyancy is controlled by adjusting the volume of air in the Buoyancy Compensation Device and, if worn and this depends on the divers mass and body composition, buoyancy of other diving gear worn, water salinity, and water temperature. It normally is in the range of 2 kilograms to 15 kilograms, the weights can be distributed to trim the diver to suit the purpose of the dive. Free divers may also use weights to counteract buoyancy of a wetsuit, as they have no decompression obligation, they do not have to be neutrally buoyant near the surface at the end of a dive. Dropping weights increases the risk of barotrauma and decompression sickness due to the possibility of an ascent to the surface. The weights are made of lead because of its high density, reasonably low cost, ease of casting into suitable shapes. The lead can be cast in blocks, cast shapes with slots for straps, or shaped as pellets often named shot, there is some concern that lead diving weights may constitute a toxic hazard to users and environment. The primary function of diving weights is as ballast, to prevent the diver from floating at times when he or she wishes to remain at depth. The weights are used mainly to neutralise the buoyancy of the suit, as the diver is nearly neutral in most cases. The weights required depend almost entirely on the buoyancy of the suit, as a corollary to this practice, freedivers will use as thin a wetsuit as comfortably possible, to minimise buoyancy changes with depth due to suit compression. Buoyancy control is considered both a skill and one of the most difficult for the novice to master. Lack of proper buoyancy control is likely to disturb or damage the surroundings, and is a source of additional and unnecessary effort to maintain precise depth. The scuba diver generally has an operational need to control depth without resorting to a line to the surface or holding onto a structure or landform, a further requirement for scuba diving in most circumstances, is the ability to achieve significant positive buoyancy at any point of a dive. When at the surface, this is a procedure to enhance safety and convenience. The average human body with a lungful of air is close to neutral buoyancy. If the air is exhaled, most people will sink in fresh water and this is usually the case with people with a large proportion of body fat. As the diver is nearly neutral, most ballasting is needed to compensate for the buoyancy of the divers equipment, the main components of the average scuba divers equipment which are positively buoyant are the components of the exposure suit. The two most commonly used exposure suit types are the dry suit and the wet suit, both of these types of exposure suit use gas spaces to provide insulation, and these gas spaces are inherently buoyant

66.
Swimfin
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Very long fins and monofins used by freedivers as a means of underwater propulsion do not require high frequency leg movement. This improves efficiency and helps to minimize oxygen consumption, short, stiff-bladed fins are effective for short bursts of acceleration and maneuvering, and are useful for bodysurfing. Early inventors, including Leonardo da Vinci and Giovanni Alfonso Borelli, modern swimfins are an invention from the Frenchman Louis de Corlieu, capitaine de corvette in the French Navy. In 1914 De Corlieu made a demonstration of his first prototype for a group of navy officers, Yves le Prieur among them who, years later in 1926. De Corlieu left the French Navy in 1924 to fully devote himself to his invention, in April 1933 he registered a patent and called this equipment propulseurs de natation et de sauvetage. After struggling for years, even producing his fins in his own flat in Paris, the same year he issued a licence to Owen Churchill for mass production in the United States. To sell his fins in the USA Owen Churchill changed the French De Corlieus name to swimfins, Churchill presented his fins to the US Navy, which decided to acquire them for its Underwater Demolition Team. American UDT and British COPP frogmen used the Churchill fins during all prior underwater deminings, during the years after World War II had ended, De Corlieu spent time and efforts struggling in civil procedures, suing others for patent infringement. In 1946 Lillywhites imported about 1,100 pairs of swimfins, in 1948 Luigi Ferraro, collaborating with the Italian diving equipment company Cressi-sub, designed the first full-foot fin, the Rondine, named after the Italian word for swallow. A distinctive feature of Cressis continuing Rondine full-foot fin line is the outline of the bird on the foot pockets. In 1949 Ivor Howitt or a friend of his mailed to the Dunlop Rubber Company for swimfins, Dunlop answered that they had no plans to make swimfins, Howitt made his own swimfins with innertube rubber stretched across a frame of stiff rubber tube. Types of fins have evolved to address the requirements of each community using them, recreational snorkellers generally use lightweight flexible fins. Free divers favour extremely long fins for efficieny of energy use, scuba divers need large wide fins to overcome the water resistance caused by their diving equipment, and short enough to allow acceptable maneuvering. Ocean swimmers, bodysurfers, and lifeguards favour smaller designs that stay on their feet when moving through large surf, the structure of a swimfin comprises a blade for propulsion and a means of attaching the blade to the foot of the wearer. The vast majority of fins come as a pair, one fin is worn on each foot and this arrangement is also called bifins, to distinguish it from monofins. A monofin is used in finswimming and free-diving and it consists of a single fin blade attached to twin foot pockets for both the divers feet. Monofins and long bifin blades can be made of fibre or carbon fibre composites. The divers muscle power and swimming style, and the type of activity the fins are used for, determine the choice of size, stiffness, and materials

Swimfin
–
Full foot fins
Swimfin
–
An assortment of fins in a diving shop. Fins on the right are full foot and those in the middle are open heel.
Swimfin
–
A monofin and pair of free diving bifins owned by the same diver
Swimfin
–
An open-heel vented paddle Jetfin

67.
Moon pool
–
It is an opening in the floor or base of the hull, platform, or chamber giving access to the water below, allowing technicians or researchers to lower tools and instruments into the sea. It provides shelter and protection so that if the ship is in high seas or surrounded by ice. A moon pool also allows divers or small craft to enter or leave the water easily. Moon pools originated in the oil drilling industry, which uses them in drilling at sea or in lakes, drill pipes need to run vertically through the structure or hull and the moon pool provides the means to do this. Very deep moon pools are used in underwater habitats—submerged chambers used by divers engaged in research, exploration, marine salvage. In this case, shown in part D of the diagram, submerged chambers provide dry areas for work and rest without the need to ascend to the surface. This kind of submerged chamber uses the principles as the diving bell, except they are fixed to the seafloor. Sometimes the term moon pool is used to mean the complete chamber, not just the opening in the bottom, Underwater habitats may have connected chambers with moon pools and lock-out chambers. SEALAB II Aquarius, Florida has a pool in one of its three chambers, called the wet porch. Diving bell Diving support vessel Underwater habitat

Moon pool
–
Underside of the Research Vessel Western Flyer, showing its moon pool between the two hulls.
Moon pool
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NEEMO 13 Crew in the wet porch/moon pool of the Aquarius habitat
Moon pool
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Modes

68.
Pony bottle
–
A pony bottle is a small diving cylinder which is fitted with an independent regulator, and carried by a scuba diver as an extension to the scuba set. The key attribute of a bottle is that it provides a totally independent and redundant source of breathing gas for the diver. The name pony is due to the size, often of only a few litres capacity. They are carried by the diver in one of several configurations. In a pony bottle system the regulator is a complete diving regulator on a separate cylinder which is not intended for use as primary breathing gas during the dive. It provides a totally redundant emergency air supply, the pony cylinder capacity will depend on the profile for safe ascent to the surface required for a particular dive plan. Popular sizes for a pony bottle include 6,13 or 19 cu ft in the USA, for deep or deep technical diving or wreck diving 30 and 40 cu ft cylinders are often used. The pony bottle is a requirement for low risk solo diving if the dive is too deep for a safe free ascent. Several scuba manufacturers produce a minimalist backpack harness that supports a back mounted pony sized bottle exclusively for use in shallow water diving or for maintenance purposes. There are several options for the mounting of a pony bottle, the most common way pony bottle is carried is by fixing it to the side of the primary scuba cylinder by straps or clamps, which may include a quick-release system. The most common alternative is slinging it between two D-rings on the divers harness or buoyancy compensator. Another possibility is to mount the bottle in a carrying bag. This affords the opportunity of handing off the system to a buddy diver if that buddy needs to share air. This is a safer procedure than the buddies having to have to be connected through use of hosed regulators. The addition of a bottle to the divers equipment will add an off-balanced weight to the side on which it is mounted. To compensate for this an equal balancing weight is added to the tank band on the opposite side of the pony. Attention must also be paid to where the pony bottle second stage regulator is placed during the pre-dive buddy check, the pony bottle is intended for use in bail out situations – situations in which the dive must be aborted and safe return to the surface must be facilitated. There are several solutions to providing such a redundant gas supply for bail out purposes which are in common use in diving

69.
Scuba set
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A scuba set is any breathing apparatus that is carried entirely by an underwater diver and provides the diver with breathing gas at the ambient pressure. Rebreather scuba recycles the exhaled gas, removes carbon dioxide, the amount of gas lost from the circuit during each breathing cycle depends on the design of the rebreather and depth change during the breathing cycle. Gas in the circuit is at ambient pressure, and stored gas is provided through regulators or injectors. The most immediate risk associated with scuba diving is drowning due to a failure of the gas supply. This may be managed by diligent monitoring of remaining gas, adequate planning, the word SCUBA was coined in 1952 by Major Christian Lambertsen who served in the U. S. Army Medical Corps from 1944 to 1946 as a physician. Lambertsen first called the closed circuit rebreather apparatus he had invented Laru, as with radar, the acronym scuba has become so familiar that it is generally not capitalized and is treated as an ordinary noun. For example, it has been translated into the Welsh language as sgwba, a diver uses a self-contained underwater breathing apparatus to breathe underwater. Scuba provides the diver with the advantages of mobility and horizontal range far beyond the reach of a hose attached to surface-supplied diving equipment. Surface supplied divers may be required to carry scuba as a breathing gas supply to get them to safety in the event of a failure of surface gas supply. There are divers who work, full or part-time, in the diving community as instructors, assistant instructors, divemasters. Other specialist areas of diving include military diving, with a long history of military frogmen in various roles. Their roles include direct combat, infiltration behind enemy lines, placing mines or using a manned torpedo, in some cases diver rescue teams may also be part of a fire department, paramedical service or lifeguard unit, and may be classed as public service diving. The choice between scuba and surface supplied diving equipment is based on legal and logistical constraints. Where the diver requires mobility and a range of movement, scuba is usually the choice if safety. Higher risk work, particularly in commercial diving, may be restricted to surface supplied equipment by legislation, there are alternative methods that a person can use to survive and function while underwater, currently including, free-diving - swimming underwater on a single breath of air. Snorkeling - a form of free-diving where the mouth and nose can remain underwater when breathing. Some tourist resorts now offer a surface-supplied diving arrangement, trademarked as Snuba, atmospheric diving suit - an armored suit which protects the diver from the surrounding water pressure. A scuba set is characterized by full independence from the surface during use, early attempts to reach this autonomy from the surface were made in the 18th century by the Englishman John Lethbridge, who invented and successfully built his own underwater diving machine in 1715

70.
Snuba
–
Snuba is form of surface-supplied diving that uses an underwater breathing system developed by Snuba International. The word snuba is a portmanteau of snorkel and scuba, the swimmer uses swimfins, a diving mask, weights, and diving regulator as in scuba diving. Instead of coming from tanks strapped to the back, air is supplied from long hoses connected to compressed air cylinders contained in a specially designed flotation device at the surface. Snuba often serves as a form of diving, in the presence of a professionally trained guide. The snuba system was devised in 1989 by California diver Michael Stafford and it was then developed and patented in 1990 by Snuba International, based in Diamond Springs, California, who own the trademark and license it as a touring program. Snuba diving is a popular guided touring activity in tropical tourist locations such as Hawaii, Thailand, Snuba is also popular because no certification or prior dive experience is required. Participants need only to be at least eight years of age, have a basic swimming ability and its popularity as a first timers experience can be attributed to several factors. The participant tows the raft on the surface via a lightweight harness connected to the air line, by utilizing the hose as a guide, combined with wearing soft weights to achieve neutral buoyancy, participants are able to descend anywhere from just under the surface to 6 metres deep. Participants are able to hold on to the raft at the using a lanyard that runs the length of the raft on both sides. This also allows the user to hold on to the raft while becoming comfortable breathing before beginning to descend. Being connected to the raft also provides users with a feeling of safety, comfort, compared to scuba, snuba divers wear minimal gear. Each diver is equipped with a mask, fins, weight belt, harness, the harness holds the regulator and air line in place, allowing the diver to swim unencumbered beneath the surface. This may be compared to full scuba gear, which includes a buoyancy compensator, weights, cylinder and often more, although scuba equipment is nearly weightless underwater, out of the water the weight becomes a significant factor for weaker individuals. In strong current, wave action, or breeze, the combination of underwater hose, Snuba is therefore best used in areas where wind, waves and current are negligible. Since all snuba use is offered by licensed snuba operators who operate the systems as a guided tour, however it is beneficial if one employee of the snuba operator remains on the surface to monitor conditions. Since the depth of a dive is limited to about 6 metres. This danger is avoided by breathing normally and continuously while ascending. This point is covered in snuba pre-dive briefings, and monitored by the dive guide throughout the dive by watching for the continual release of bubbles from each diver

Snuba
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Breathing air is supplied through hoses from a raft
Snuba
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Air is supplied from a tank on a raft

71.
Towboard
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A towboard is a piece of aquatic survey equipment consisting of a board attached to a rope that is towed by a surface vessel. It is used to tow one or more divers underwater at a constant depth to survey bottom features such as coral reefs, the diver may use a scuba set, or if only a snorkel, may remain at the surface, or travel underwater for around two minutes. The towing vessel travels at approximately 1 to 2 miles per hour, the boat follows a depth contour to keep the towboard over a specific depth. The divers can also maneuver the board to maintain a precise depth. A survey may cover up to nearly 2 miles over a period of around 50 minutes. This type of surveying method is called a towboard survey, towed-diver survey, and the manta tow technique, the named after the Manta Board. A variant is the SAM or Single-armed Manta-board and this consists of a small board with a strap to secure and tow the diver by the forearm. This frees the other arm, allowing the diver to take notes on a pad held by the towing arm, the use of a towboard is considered safe for NOAA reef surveys by trained divers at depths where no decompression stops are required. Towboards may be equipped with sensors to record the temperature and depth every few seconds, position of the diver is approximate and must be calculated from the boat position, heading and towline length. Crown-of-thorns starfish and coral surveys using the tow and scuba search techniques

72.
Wetsuit
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The insulation properties depend on bubbles of gas enclosed within the material, which reduce its ability to conduct heat. The bubbles also give the wetsuit a low density, providing buoyancy in water, hugh Bradner, a University of California, Berkeley physicist invented the modern wetsuit in 1952. Further improvements in the seals at the neck, wrists, ankles, different types of wetsuit are made for different uses and for different temperatures. Suits range from a thin shortie, covering just the torso, to a full 8 mm semi-dry, usually complemented by neoprene boots, gloves and hood. Activities include underwater diving, sailing, sea rescue operations, surfing, river rafting, whitewater kayaking and in some circumstances, endurance swimming. In open water swimming events the use of wetsuits is controversial, as some claim that wetsuits are being worn for competitive advantage. This varies by locales and times of the year, where temperatures are substantially below comfortable. Still water conducts heat away from the body by pure thermal diffusion, Wetsuits are made of closed-cell, foam neoprene, a synthetic rubber that contains small bubbles of nitrogen gas when made for use as wetsuit material. Uncompressed foam neoprene has a thermal conductivity in the region of 0.054 Wm−1K−1. However at a depth of 15 metres of water, the thickness of the neoprene will be halved and its conductivity will be increased by 50%, allowing heat to be lost at three times the rate at the surface. A wetsuit must have a fit to work efficiently when immersed, too loose a fit. Flexible seals at the suit cuffs aid in preventing heat loss in this fashion, foamed neoprene is very buoyant, helping swimmers to stay afloat, and for this reason divers need to carry extra weight based on the volume of their suit to achieve neutral buoyancy near the surface. However, the suit loses buoyancy and thermal protection as the bubbles in the neoprene are compressed at depth, semi-dry suits are effectively a wetsuit with reasonably effective seals at wrist, neck, ankles and zipper. The seals limit the amount of entering and leaving the suit. The wearer gets wet in a suit but the water that enters is soon warmed up and does not leave the suit readily. The trapped layer of water does not add significantly to the insulating ability. Any residual water circulation past the seals still causes heat loss, semi-dry suits are cheap and simple compared to dry suits. They are usually made from thick Neoprene, which provides thermal protection at shallow depth

73.
Clearance diver
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In some navies, including Britains Royal Navy, work divers, which includes Ships divers, must have a line and a linesman when possible. The first units were Royal Navy Mine and Bomb Disposal Units and they were succeeded by the Port Clearance Parties. The first operations by P Parties included clearing away the debris of unexploded ammunition left during the Normandy Invasion, six groups of Clearance Divers including Commonwealth and European allied forces were in operation by 1945. Naval work diver training is longer and harder than sport diver training and has much stricter entry requirements. For a long time used the heavy standard diving dress for underwater work. During and after World War II some of them started using frogman-type gear when frogmans kit became available, later they started often using open-circuit scuba gear for work diving. The Royal Australian Navy Clearance Diving Branch clearance divers also serve as combat divers, the Royal New Zealand Navy Operational Diving Team are clearance divers and also serve as combat divers. Canada, Canadian armed forces divers US, Underwater Demolition Team - US Navy, 1943–1967 Estonia, EOD Tuukrigrupp France, germany, Minentaucher is Germanys Clearance Diver force. Lithuania, EOD Diving unit Norway, Minedykkerkommandoen Norways naval work divers and Clearance Diver force, portugal, the Sapper Divers Group, which also serve as combat divers unit. Sweden, Swedish Navy EOD division British Royal Navy naval work divers are officially called Clearance Divers, during WWII they at first often used the Davis Submerged Escape Apparatus and no diving suit, and no swimfins and they swam by breaststroke. On 1942 December 17,6 Italians on three manned torpedoes attacked Gibraltar harbor, a British patrol boat killed one torpedos crew with a depth charge. Their bodies were recovered, and their swimfins were taken and used by two of Gibraltars British guard divers and this was the first known British frogman use of swimfins, rather than a Sladen suit and weighted boots riding a Chariot. He also brought them an Italian light 2-piece frogmans drysuit, before then they dived with their skin exposed, for many years Clearance Divers used the Siebe Gorman CDBA rebreather. In 1982 Clearance Divers were heavily involved in the Falklands War and they received many awards and medals for their work on mines and disposing of 1000-pound bombs lodged in British warships. Other combinations of kit used in the past by British Clearance Divers were, Sladen suit and weighted boots, Sladen suit and weighted boots and aqualung. According to a 1950s British naval diving manual, this was the approved way to use the aqualung. Presently, Fleet Diving Units 2 and 3 are the main clearance divers of the Royal Navy, Fleet Diving Unit 1 is also focused on clearance, specifically terrorist devices. US military divers US Navy diver US Navy EOD Frogman, someone who is trained as a combat diver

Clearance diver
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A US Navy work diver is lowered to the sea bed during a dive from the USNS Grasp (ARS 51) off the coast of St. Kitts.
Clearance diver
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Preparing to raise a mine from the seabed
Clearance diver
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US Navy explosive ordnance disposal (EOD) divers
Clearance diver
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Modes

74.
Commercial offshore diving
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The work in this area of the industry includes maintenance of oil platforms and the building of underwater structures. In this context offshore implies that the work is done outside of national boundaries. Equipment used for offshore diving tends to be surface supplied equipment but this varies according to the work, for instance, divers in the Gulf of Mexico may use wetsuits whilst North Sea divers need dry suits or even hot water suits because of the low temperature of the water. Diving work in support of the oil and gas industries is usually contract based. Saturation diving is standard practice for bottom work at many of the deeper offshore sites, surface oriented air diving is more usual in shallower water. The offshore diver may do a range of tasks in support of offshore drilling or production. Much of the offshore seabed diving work is inspection, maintenance and repair of the blow-out preventers, there are a wide range of production platforms which are chosen to suit the water depth, expected sea conditions and other constraints. Diving work will depend on the details, but will generally involve inspection, maintenance and repair of the structure, wellheads, manifolds, risers, associated pipelines and mooring systems. Divers may work on marine risers and blowout prevention stacks on all production rig types if the depth is within diving range, work may be surface oriented or in saturation depending on depth and duration. Depths are relatively shallow on jack-up rigs, which stand on the seabed, much of the diving may be on air. Semi-submersible platforms operate in a range of depths, mostly relatively deep. There is also work on the hull which is likely to be on air, inspection of thrusters, pontoons and the rest of the underwater structure of the rig. Wellheads control the production of oil or gas from the well and they are mounted on production guidebases, which are the upper endpoint of the well casing at the seabed. A well head can be connected to a subsea manifold or indirectly via other wellheads. Most diving work on wellheads and manifolds is installation and maintenance, subsea manifolds are structures mounted on the seabed where pipelines and connections to wellheads are connected to control the flow of product from the wells to their next destination. A large amount of offshore diving work is associated with pipeline work, depths may range from deep to shallow, and procedures and diving mode will be chosen to suit. Work includes aspects of pipe laying and trenching, and work on existing pipelines, as the pipe approaches the seabed, the pipe takes a convex-downward curve before making contact with the bottom. The sagbend is controlled by tension applied from the vessel and tension wires from the pipeline on the bottom to anchors which prevent it from being dragged out of position by the barge

75.
Diver training
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Recreational diver training is the process of developing skills and knowledge in the use of diving equipment and techniques so that the diver is able to dive with minimum risks. Not only is the underwater environment hazardous but diving equipment can be dangerous, most commercial operators and dive clubs serving divers insist that each diver is able to show them certification, for the type of diving the diver intends to do. Dive operators, dive shops, and compressor operators on occasion have been known to refuse to allow uncertified people to dive, diving instructors affiliated to a diving certification agency may work independently or through a university, a dive club, a dive school or a dive shop. They will offer courses that should meet, or exceed, the standards of the organization that will certify the divers attending the course. Reliable and unbiased advice on how to find quality diving instruction can be difficult to come by, there are computer bulletin boards such as ScubaBoard that, at their best provide sterling advice, How to find an excellent SCUBA class, but that at their worst can be misleading. The initial open water training for a person who is fit to dive. Many dive shops in popular holiday locations offer courses intended to teach a novice to dive in a few days, other instructors and dive schools will provide more thorough training, which generally takes longer. Initial training typically takes place in three environments, Classroom - where material is presented and reviewed Confined Water - where skills are taught, Open Water - where the student demonstrates and refines the skills he or she has learned. Typically, early open water training takes place in a body of water such as a lake. Advanced training mostly takes place at depths and locations similar to the divers normal diving locations, BSAC allows 6-year-olds to train for the Dolphin Snorkeller grade. From the age of 8 years old PADI has the SEAL Team program, PADI allows 10-year-olds to do the full Open Water Diver course. They are called Junior Open Water divers, there are restrictions on their depth and group size when diving. Also they must dive with their parents or a professional, when they reach the age of 12 they can dive with a qualified adult. Over 15 they are considered capable of diving with others of the age or above. BSAC allows 12-year-olds to do the full entry level diving course - the Ocean Diver course and this qualification has no restrictions for the young diver, but individual branches of BSAC are free to set their own minimum age for branch membership. The International Organization for Standardization has approved six recreational diving standards that may be implemented worldwide, the listed standards developed by the RSTC are consistent with the applicable ISO Standards, List of diver certification organizations Scuba Diver Training Agencies at DMOZ

76.
Police diving
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Police diving is a branch of professional diving carried out by police services. The duties carried out by police divers include rescue diving for underwater casualties and search and recovery diving for evidence and these divers are typically members of police departments, sheriffs offices, fire rescue agencies, search and rescue teams or providers of emergency medical services. Public Safety Divers can be paid by the previously mentioned agencies or non-paid volunteers, a fictional example of a police diver is Eric Delko from the CBS crime drama CSI, Miami. Although these are courses for improving someone’s diving skills and further progressing in diving education they are not professional courses. However many professional courses would expect a participant to have progressed to that level in the recreational diving before becoming a professional. The National Academy of Police Diving was formed in 1988 by a group of divers to create a national standard for police and public safety diver training. Diving activities Professional diving Public safety diving Naui Worldwide Public Safety Dive Certification

77.
Professional diving
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Professional diving is diving where the divers are paid for their work. There are also applications in research, Marine archaeology, fishing and aquaculture, public service and law enforcement. Due to the nature of some professional diving operations, specialized equipment such as an on-site hyperbaric chamber. In many cases a statutory national occupational health and safety legislation constrains their activities, the purpose of recreational diving is basically for personal entertainment, while the professional diver has a job to do, and diving is necessary to get that job done. The work in area of the industry includes maintenance of oil platforms. Equipment used for offshore diving tends to be surface supplied equipment but this does vary depending on the nature of the work, for instance Gulf of Mexico-based divers may use wetsuits whilst North Sea divers need drysuits or even hot water suits due to the temperature of the water. They are often required to inspect and repair outfalls which require at times up to 600 ft. plus penetrations, onshore divers typically can be at home every night and earn more per hour than their colleagues who work offshore. However, depth pay and minimum 12-hour shifts offshore must be taken into consideration, the equipment used does depend on the nature of the work and location, but normally a mixture of SCUBA and surface-supplied diving equipment is used by divers and their employers. HAZMAT diving is one of the most dangerous branches of the diving industry. Typical work involves diving into raw sewage or dangerous chemicals, such as pulp, liquid cement. This leads to special requirements, The divers need to be vaccinated against diseases such as hepatitis, suitable equipment and competent personnel are required for decontamination of the diver and diving equipment after a dive. Emergency procedures must be planned and equipment and personnel in place to recover the diver if something goes wrong. The tasks a diver may be required to do in a contaminated environment include, Essential maintenance of underwater valves, pollution control work to contain, control and clean up after a pollution incident. Sampling activities, such as performed by United States Environmental Protection Agency. Units specializing in polluted water diving, such as Region 10, Diving in landfill sites to maintain the pumping equipment, vital in preventing landfill sites from filling up with rainwater and contaminating the water table. Welding inside functioning sewers or working in septic tanks, miscellaneous repairs and finding lost objects. Divers working in a contaminated environment wear a full drysuit with integral boots. Cut-resistant dry-gloves and helmet will seal directly to the drysuit, leaving no skin exposed to the environment, the risk of leakage through the exhaust valve of a demand system can be reduced in three ways

Professional diving
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A US Navy diver at work. The umbilical supplying air from the surface is clearly visible.
Professional diving
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Surface supplied commercial diving equipment on display at a trade show
Professional diving
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Inshore diving commonly includes underwater work in support of construction projects
Professional diving
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US Navy Diver being decontaminated after a dive

78.
Public safety diving
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Police diving is a branch of professional diving carried out by police services. The duties carried out by police divers include rescue diving for underwater casualties and search and recovery diving for evidence and these divers are typically members of police departments, sheriffs offices, fire rescue agencies, search and rescue teams or providers of emergency medical services. Public Safety Divers can be paid by the previously mentioned agencies or non-paid volunteers, a fictional example of a police diver is Eric Delko from the CBS crime drama CSI, Miami. Although these are courses for improving someone’s diving skills and further progressing in diving education they are not professional courses. However many professional courses would expect a participant to have progressed to that level in the recreational diving before becoming a professional. The National Academy of Police Diving was formed in 1988 by a group of divers to create a national standard for police and public safety diver training. Diving activities Professional diving Public safety diving Naui Worldwide Public Safety Dive Certification

79.
Recreational diving
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Recreational diving or sport diving is diving for the purpose of leisure and enjoyment, usually when using scuba equipment. Risk is managed by training the diver in a range of standardised procedures and skills appropriate to the equipment the diver chooses to use, further experience and development of skills by practice will increase the divers ability to dive safely. Specialty training is available by the recreational diver training industry and diving clubs to increase the range of environments. Recreational scuba diving out of related activities such as Snorkeling. For a long time, recreational underwater excursions were limited by breath-hold time, as the sport became more popular, manufacturers became aware of the potential market, and equipment began to appear that was easy to use, affordable and reliable. The first scuba diving school was opened in France to train the owners of the Cousteau, the first school to teach single hose scuba was started in 1953, in Melbourne, Australia, at the Melbourne City Baths. RAN Commander Batterham organized the school to assist the inventor of the single hose regulator, however, neither of these schools was international in nature. There were no training courses available to civilians who bought the early scuba equipment. Professional instruction started in 1959 when the non-profit NAUI was formed, the National Association of Scuba Diving Schools started with their dive center based training programs in 1962 followed by SSI in 1970. Professional Diving Instructors College was formed in 1965, changing its name in 1984 to Professional Diving Instructors Corporation, in 2009 PADI alone issued approximately 950,000 diving certifications. Approximately 550,000 of these PADI certifications were entry level certifications, scuba-diving has become a popular leisure activity, and many diving destinations have some form of dive shop presence that can offer air fills, equipment, and training. In tropical and sub-tropical parts of the world, there is a market for holiday divers, people who train and dive while on holiday. Technical diving and the use of rebreathers are increasing, particularly in areas of the world where deeper wreck diving is the underwater attraction. It has been observed that leisure divers are often inexperienced, either under-trained or over-certified, divers are instructed and assessed on these skills during basic and advanced training, and are expected to remain competent at their level of certification, either by practice or refresher courses. This allows divers trained by the various certifying organisations to dive together with a minimum of confusion, diver communications is a particular aspect where most of the basic hand signals are common to most recreational diver training agencies. This does not mean there is no variation. Length of regulator hose and position of the second stage depend on the donation technique. There are also variations in procedures for rescue in an out of air situation

80.
Scientific diving
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Professional diving is diving where the divers are paid for their work. There are also applications in research, Marine archaeology, fishing and aquaculture, public service and law enforcement. Due to the nature of some professional diving operations, specialized equipment such as an on-site hyperbaric chamber. In many cases a statutory national occupational health and safety legislation constrains their activities, the purpose of recreational diving is basically for personal entertainment, while the professional diver has a job to do, and diving is necessary to get that job done. The work in area of the industry includes maintenance of oil platforms. Equipment used for offshore diving tends to be surface supplied equipment but this does vary depending on the nature of the work, for instance Gulf of Mexico-based divers may use wetsuits whilst North Sea divers need drysuits or even hot water suits due to the temperature of the water. They are often required to inspect and repair outfalls which require at times up to 600 ft. plus penetrations, onshore divers typically can be at home every night and earn more per hour than their colleagues who work offshore. However, depth pay and minimum 12-hour shifts offshore must be taken into consideration, the equipment used does depend on the nature of the work and location, but normally a mixture of SCUBA and surface-supplied diving equipment is used by divers and their employers. HAZMAT diving is one of the most dangerous branches of the diving industry. Typical work involves diving into raw sewage or dangerous chemicals, such as pulp, liquid cement. This leads to special requirements, The divers need to be vaccinated against diseases such as hepatitis, suitable equipment and competent personnel are required for decontamination of the diver and diving equipment after a dive. Emergency procedures must be planned and equipment and personnel in place to recover the diver if something goes wrong. The tasks a diver may be required to do in a contaminated environment include, Essential maintenance of underwater valves, pollution control work to contain, control and clean up after a pollution incident. Sampling activities, such as performed by United States Environmental Protection Agency. Units specializing in polluted water diving, such as Region 10, Diving in landfill sites to maintain the pumping equipment, vital in preventing landfill sites from filling up with rainwater and contaminating the water table. Welding inside functioning sewers or working in septic tanks, miscellaneous repairs and finding lost objects. Divers working in a contaminated environment wear a full drysuit with integral boots. Cut-resistant dry-gloves and helmet will seal directly to the drysuit, leaving no skin exposed to the environment, the risk of leakage through the exhaust valve of a demand system can be reduced in three ways

Scientific diving
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A US Navy diver at work. The umbilical supplying air from the surface is clearly visible.
Scientific diving
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Surface supplied commercial diving equipment on display at a trade show
Scientific diving
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Inshore diving commonly includes underwater work in support of construction projects
Scientific diving
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US Navy Diver being decontaminated after a dive

81.
Underwater archaeology
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Underwater archaeology is archaeology practiced underwater. As with all branches of archaeology, it evolved from its roots in pre-history. As a result, underwater archaeology initially struggled to establish itself as bona fide archaeological research, the situation changed when universities began teaching the subject and when a theoretical and practical base for the sub-discipline was firmly established. This is most often effected using the remains found in. In recent years, the study of submerged WWII sites and of submerged aircraft in the form of aviation archaeology have also emerged as bona fide activity. Though often mistaken as such, underwater archaeology is not restricted to the study of shipwrecks. At the end of the last ice age, the North Sea was a great plain, also, because human societies have always made use of water, sometimes the remains of structures that these societies built underwater still exist when traces on dry land have been lost. The archaeological signature at this also now extends into the interaction between indigenous people and the European pastoralists who entered the area in the mid-19th century. There are many reasons why underwater archaeology can make a significant contribution to our knowledge of the past, in the shipwreck field alone, individual shipwrecks can be of significant historical importance either because of the magnitude of loss of life or circumstances of loss. All traces of human existence underwater which are one hundred years old or more are protected by the UNESCO Convention on the Protection of the Underwater Cultural Heritage and this convention aims at preventing the destruction or loss of historic and cultural information and looting. It helps states parties to protect their cultural heritage with an international legal framework. Underwater sites are difficult to access, and more hazardous. In order to access the site directly, diving equipment and diving skills are necessary, the depths that can be accessed by divers, and the length of time available at depths, are limited. For deep sites beyond the reach of divers, submarines or remote sensing equipment are needed, for a marine site, while some form of working platform is often needed, shore-based activities are common. Notwithstanding, underwater archaeology is a field plagued by logistics problems, equipment used for archaeological investigation, including water dredge and air lifts create additional hazards and logistics issues. Moreover, marine sites may be subject to strong tidal flows or poor weather which mean that the site is accessible for a limited amount of time. Some marine creatures also pose a threat to diver safety, Underwater sites are often dynamic, that is they are subject to movement by currents, surf, storm damage or tidal flows. Structures may be uncovered, or buried beneath sediments

Underwater archaeology
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Drawing to scale, underwater
Underwater archaeology
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Rock house settlement seen on left in 1927 while Lake Murray (South Carolina) was under construction, middle and right are two angles of aspect on Side-scan sonar in 100 ft of fresh water under the lake in 2005
Underwater archaeology
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Wreck of E. Russ in Estonia is considered as a national heritage monument.
Underwater archaeology
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LAMP archaeologist recording a scaled drawing of the ship's bell discovered on the late 18th century "Storm Wreck" off St. Augustine, Florida

82.
High-pressure nervous syndrome
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High-pressure nervous syndrome is a neurological and physiological diving disorder that results when a diver descends below about 500 feet using a breathing gas containing helium. The effects experienced, and the severity of effects, depend on the rate of descent. Helium tremors were first widely described in 1965 by Royal Navy physiologist Peter B, bennett, who also founded the Divers Alert Network. Russian scientist G. L. Zaltsman also reported on helium tremors in his experiments from 1961, however, these reports were not available in the West until 1967. Symptoms of HPNS include tremors, myoclonic jerking, somnolence, EEG changes, visual disturbance, nausea, dizziness, HPNS has two components, one resulting from the speed of compression and the other from the absolute pressure. The compression effects may occur when descending below 500 feet at rates greater than a few metres per minute, the effects from depth become significant at depths exceeding 1,000 feet and remain regardless of the time spent at that depth. The susceptibility of divers and animals to HPNS varies over a wide range depending on the individual and it is likely that HPNS cannot be entirely prevented but there are effective methods to delay or change the development of the symptoms. Utilizing slow rates of compression or adding stops to the compression have been found to prevent large initial decrements in performance, including other gases in the helium–oxygen mixture, such as nitrogen or hydrogen suppresses the neurological effects. Alcohol, anesthetics and anticonvulsant drugs have had varying results in suppressing HPNS with animals, none are currently in use for humans. Nitrogen narcosis Decompression sickness Select publications about HPNS hosted by the Rubicon Foundation

83.
Isobaric counterdiffusion
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In physiology, isobaric counterdiffusion is the diffusion of different gases into and out of tissues while under a constant ambient pressure, and the physiological effects of this phenomenon. The term inert gas counterdiffusion is sometimes used as a synonym, in medicine, ICD is the diffusion of gases in different directions that can increase the pressure inside open air spaces of the body and surrounding equipment. An example of this would be a patient breathing nitrous oxide in an operating room, cuffs on the endotracheal tubes must be monitored as nitrous oxide will diffuse into the air filled space causing the volume to increase. In laparoscopic surgery, nitrous oxide is avoided since the gas will diffuse into the abdominal or pelvic cavities causing an increase in internal pressure, in the case of a tympanoplasty, the skin flap will not lay down as the nitrous oxide will be diffusing into the middle ear. In underwater diving, ICD is the diffusion of one inert gas into body tissues while another inert gas is diffusing out, an example of this would be breathing air in an heliox environment. The helium in the heliox diffuses into the skin quickly, while the nitrogen diffuses more slowly from the capillaries to the skin, the resulting effect generates supersaturation in certain sites of the superficial tissues and the formation of inert gas bubbles. These isobaric skin lesions do not occur when the ambient gas is nitrogen, deep tissue ICD occurs when different inert gases are breathed by the diver in sequence. The rapidly diffusing gas is transported into the faster than the slower diffusing gas is transported out of the tissue. An example of this was shown in the literature by Harvey in 1977 as divers switched from a mixture to a helium mixture. Saturation divers breathing hydreliox switched to a mixture and developed symptoms of decompression sickness during Hydra V. It can also happen when saturation divers breathing hydreliox switch to a heliox mixture and this model suggests that diffusion of gases from the middle ear across the round window is negligible. The model is not necessarily applicable to all tissue types, lambertsen made suggestions to help avoid ICD while diving. If the diver is surrounded by or saturated with nitrogen, they should not breathe helium rich gases, however Doolette and Mitchells more recent study of Inner Ear Decompression Sickness now shows that the inner ear may not be well-modelled by common algorithms. Recompression with oxygen is effective for relief of symptoms resulting from ICD, however, Burtons model for IEDCS does not agree with Doolette and Mitchells model of the inner ear. Doolette and Mitchell model the inner ear using solubility coefficients close to that of water, switches should also be made during breathing of the largest inspired oxygen partial pressure that can be safely tolerated with due consideration to oxygen toxicity. This could cause immediate bubble formation and growth in the fast tissues and this rule has been found to successfully avoid ICD on hundreds of deep trimix dives. A decompression planning software tool called Ultimate Planner attempts to predict ICD through modeling the inner ear as either aqueous or lipid tissue, Decompression sickness Decompression Breathing gas Lambertsen/ U Penn isobaric counterdiffusion references

84.
List of diving hazards and precautions
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Divers face specific physical and health risks when they go underwater with scuba or other diving equipment, or use high pressure breathing gas. Some of these factors also affect people who work in raised pressure environments out of water and this article lists hazards that a diver may be exposed to during a dive, and possible consequences of these hazards, with some details of the proximate causes of the listed consequences. A listing is given of precautions that may be taken to reduce vulnerability. A hazard that is understood and acknowledged may present a risk if appropriate precautions are taken. A hazard is any agent or situation that poses a level of threat to life, health, property, many diving fatalities are the result of a cascade of incidents overwhelming the diver, who should be able to manage any single reasonably foreseeable incident. Precisely where the line is drawn depends on circumstances, commercial diving operations tend to be less tolerant of risk than recreational, particularly technical divers, who are less constrained by occupational health and safety legislation. Decompression sickness and arterial gas embolism in recreational diving are associated with demographic, environmental. No significant associations with decompression sickness or arterial gas embolism were found for asthma, diabetes, cardiovascular disease, smoking, increased depth, previous DCI, days diving, and being male were associated with higher risk for decompression sickness and arterial gas embolism. Hazards specific to special purpose underwater tools should be described in the article for the tool, US Navy Diving Manual, 6th revision. United States, US Naval Sea Systems Command, doing it Right, The Fundamentals of Better Diving. CD-ROM prepared and distributed by the National Technical Information Service in partnership with NOAA, chung, J, Brugger, J, Curley, M, Wallick, M, Perkins, R, Regis, D, Latson, G. Health survey of U. S. Navy divers from 1960 to 1990, US Navy Experimental Diving Unit Technical Report 2011-11. Edmonds, C, Thomas, R, McKenzie, B, Pennefather, J. Diving Medicine for Scuba Divers